Simple answer would be found in Deuteronomy 14:2 For thou art an holy people unto the LORD thy God, and the LORD hath chosen thee to be a peculiar people unto himself, above all the nations that are upon the earth.
Deut 7:6 For thou art an holy people unto the LORD thy God: the LORD thy God hath chosen thee to be a special people unto himself, above all people that are upon the face of the earth.
A more in depth answer would be because God made a Covenant with Abraham. But this needs to be explained and thus we have provided many Scriptures which explain.
God chose the Hebrews, (the lineage of Abraham, Isaac and Jacob) to bring redemption to the world through Jesus Christ, the Savior-- Seed of Abraham, a Son of David. God made a Covenant with Abraham which establishes this very fact. God chose the Hebrews to be a people separated unto God. Through the Hebrews, God revealed Himself to mankind.
The Israelites were a people through whom the salvation (Messiah) would come to the whole world.
Through Abraham, God established for Himself a people who would worship the One True and Living God in the midst of universal polytheism. The Israelites were to be a witness and a light for Him in the earth. God performed many wonderful miracles in their midst. The whole world heard about the Hebrews and were afraid of "their God." God not only enabled them to win battle after battle over their enemies but the LORD fought the battles for them. Unfortunately, time and time again, they turned to other gods and worshipped idols and forgot the Lord of Heaven and by their disobedience came warnings of judgment and then after time, the judgment ... but God did not forget His covenant made with Abraham, Isaac and Jacob.
God was still faithful to His people and would forgive those who came back to Him. He sent prophets to the Israelites warning them of impending judgment. It was only in the midst of tribulation and adversity that they remembered the LORD. When their enemies were storming down the gates, then they remembered the LORD. God always keeps His promises and thus the Hebrew people remain a testimony on this earth of God's mercy and kindness and that God keeps His Covenants. No other group of people have been so persecuted, so dispersed to the far corners of the globe and yet remain so true to their heritage. The fact that the descendants of Jacob even exist at all is a testimony to God's faithfulness. (So many other peoples and nations have come and gone.) The Lord promised that He would regather His people in the Last Days and that Israel will never be conquered again and will remain forever-- but the regathering that has taken place in the past 100 years is not a fulfillment of the prophecy. That prophecy has YET TO BE FULFILLED. Israel has not yet recognized Jesus as Messiah, which necessitates what the Old Testament as well as the New Testament speaks of: a time called "Jacob's Trouble" or Daniel's 70th Week.
"The Great Tribulation" will be a terrible time for the land of Israel but in the end, the Hebrew remnant will cry out to the LORD and He will rescue them. Jesus (with His nail prints in His hands and feet)...the Messiah that they rejected 2000 years ago will come to save His people in that day which the Bible calls "the Day of the Lord."
Peter preached to the crowd and addressed God as "the God of Abraham, Isaac and Jacob:" Act 3:13-15 "The God of Abraham, and of Isaac, and of Jacob, the God of our fathers, hath glorified his Son Jesus; whom ye delivered up, and denied him in the presence of Pilate, when he was determined to let him go. But ye denied the Holy One and the Just, and desired a murderer to be granted unto you; And killed the Prince of life, whom God hath raised from the dead; whereof we are witnesses. "
When the LORD appeared to Moses in the burning bush, He said: Acts 7:32 Saying, I am the God of thy fathers, the God of Abraham, and the God of Isaac, and the God of Jacob. Then Moses trembled, and durst not behold.
Let's go back to the beginning with Abraham: Gen 12:1 Now the LORD had said unto Abram, Get thee out of thy country, and from thy kindred, and from thy father's house, unto a land that I will shew thee: Gen 12:2 And I will make of thee a great nation, and I will bless thee, and make thy name great; and thou shalt be a blessing: Gen 12:3 And I will bless them that bless thee, and curse him that curseth thee: and in thee shall all families of the earth be blessed.
All the families of the earth are blessed because of Jesus Christ, who is the seed of Abraham and the Redeemer of mankind. (Matthew chapter 1 and Luke chapter 3)
Galatians 3:8 gives the explanation: " And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed. "
Jesus said in John 8:56 "Your father Abraham rejoiced to see my day: and he saw it, and was glad. "
Romans 4:3 For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness.
Galatians 3:6-9 Even as Abraham believed God, and it was accounted to him for righteousness. Know ye therefore that they which are of faith, the same are the children of Abraham. And the Scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed. So then they which be of faith are blessed with faithful Abraham.
Gal 3:14 That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
God talks to Abraham again in Genesis chapter 17. Gen 17:7 And I will establish my covenant between me and thee and thy seed after thee in their generations for an everlasting covenant, to be a God unto thee, and to thy seed after thee.
God also blessed and established the covenant through Isaac, Abraham's second son. Gen 17:10 This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised.
Gen 17:19 And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
Romans 9:7-8 explains: "Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called. That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed. "
Abraham was a man who trusted in Lord and walked by faith. He was called the Friend of God.
Heb 11:8 By faith Abraham, when he was called to go out into a place which he should after receive for an inheritance, obeyed; and he went out, not knowing whither he went. Heb 11:9 By faith he sojourned in the land of promise, as in a strange country, dwelling in tabernacles with Isaac and Jacob, the heirs with him of the same promise: Heb 11:10 For he looked for a city which hath foundations, whose builder and maker is God. Heb 11:17 By faith Abraham, when he was tried, offered up Isaac: and he that had received the promises offered up his only begotten son, Heb 11:18 Of whom it was said, That in Isaac shall thy seed be called: Heb 11:19 Accounting that God was able to raise him up, even from the dead; from whence also he received him in a figure.
James 2:23 And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
The LORD appeared to Isaac in Genesis chapter 26:
Gen 26:2 And the LORD appeared unto him, and said, Go not down into Egypt; dwell in the land which I shall tell thee of: Gen 26:3 Sojourn in this land, and I will be with thee, and will bless thee; for unto thee, and unto thy seed, I will give all these countries, and I will perform the oath which I sware unto Abraham thy father; Gen 26:4 And I will make thy seed to multiply as the stars of heaven, and will give unto thy seed all these countries; and in thy seed shall all the nations of the earth be blessed; Gen 26:5 Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws. Gen 26:24 And the LORD appeared unto him the same night, and said, I am the God of Abraham thy father: fear not, for I am with thee, and will bless thee, and multiply thy seed for my servant Abraham's sake.
The Covenant was then established through Isaac's son, Jacob. Isaac had twin sons but the covenant was established through Jacob and not Esau.
Jacob dreamed of a ladder: Genesis 28:13 "And, behold, the LORD stood above it, and said, I am the LORD God of Abraham thy father, and the God of Isaac: the land whereon thou liest, to thee will I give it, and to thy seed; " Gen 28:14 And thy seed shall be as the dust of the earth, and thou shalt spread abroad to the west, and to the east, and to the north, and to the south: and in thee and in thy seed shall all the families of the earth be blessed.
God changed Jacob's name to Israel. Gen 32:28 And he said, Thy name shall be called no more Jacob, but Israel: for as a prince hast thou power with God and with men, and hast prevailed. Gen 32:29 And Jacob asked him, and said, Tell me, I pray thee, thy name. And he said, Wherefore is it that thou dost ask after my name? And he blessed him there. Gen 32:30 And Jacob called the name of the place Peniel: for I have seen God face to face, and my life is preserved.
Gen 35:12 And the land which I gave Abraham and Isaac, to thee I will give it, and to thy seed after thee will I give the land.
Psalm 135:4 For the LORD hath chosen Jacob unto himself, and Israel for his peculiar treasure. Isaiah 44:1 Yet now hear, O Jacob my servant; and Israel, whom I have chosen:
Jacob had 12 sons and his sons had many children who became the 12 Tribes of Israel. Through Jacob's son, Judah or sometimes spelled Juda, the Messiah would be born of his seed.
Gen 49:10 The sceptre shall not depart from Judah, nor a lawgiver from between his feet, until Shiloh come; and unto him shall the gathering of the people be.
Mat 2:5 And they said unto him, In Bethlehem of Judaea: for thus it is written by the prophet, Mat 2:6 And thou Bethlehem, in the land of Juda, art not the least among the princes of Juda: for out of thee shall come a Governor, that shall rule my people Israel.
Heb 7:14a For it is evident that our Lord sprang out of Juda; Rev 5:5 And one of the elders saith unto me, Weep not: behold, the Lion of the tribe of Juda, the Root of David, hath prevailed to open the book, and to loose the seven seals thereof.
Psalm 78:68 But chose the tribe of Judah, the mount Zion which he loved. Psalm 78:69 And he built his sanctuary like high palaces, like the earth which he hath established for ever.
Now King David was of the seed of Judah. There was a promise or Covenant given by God to David, that the LORD would establish the throne of David forever.
1Chr 17:11 And it shall come to pass, when thy days be expired that thou must go to be with thy fathers, that I will raise up thy seed after thee, which shall be of thy sons; and I will establish his kingdom. 1Chr 17:12 He shall build me an house, and I will stablish his throne for ever. 1Chr 17:13 I will be his father, and he shall be my son: and I will not take my mercy away from him, as I took it from him [Saul] that was before thee: 1Chr 17:14 But I will settle him in mine house and in my kingdom for ever: and his throne shall be established for evermore. 2Sam 7:16 And thine house and thy kingdom shall be established for ever before thee: thy throne shall be established for ever. 1Kings 8:25 Therefore now, LORD God of Israel, keep with thy servant David my father that thou promisedst him, saying, There shall not fail thee a man in my sight to sit on the throne of Israel; so that thy children take heed to their way, that they walk before me as thou hast walked before me.
Jesus is of the Seed of David. Genealogies were of strict importance in Biblical times. The Messianic lineage is meticulously recorded throughout the Old Testament and fulfilled in the New Testament.
In Matthew, chapter 1, we read: Mat 1:1 The book of the generation of Jesus Christ, the son of David, the son of Abraham. Mat 1:2 Abraham begat Isaac; and Isaac begat Jacob; and Jacob begat Judas and his brethren; Mat 1:3 And Judas begat Phares and Zara of Thamar; and Phares begat Esrom; and Esrom begat Aram; Mat 1:4 And Aram begat Aminadab; and Aminadab begat Naasson; and Naasson begat Salmon; Mat 1:5 And Salmon begat Booz of Rachab; and Booz begat Obed of Ruth; and Obed begat Jesse; Mat 1:6 And Jesse begat David the king; and David the king begat Solomon of her that had been the wife of Urias;
Luke 1:32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: John 7:42 Hath not the scripture said, That Christ cometh of the seed of David, and out of the town of Bethlehem, where David was? Rom 1:3 Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh; 2Tim 2:8 Remember that Jesus Christ of the seed of David was raised from the dead according to my gospel:
This is just a small walk through of some of the Scriptures on this subject. To sum it all up:
The Old Testament is the account of a nation, Israel. God chose the descendants of Jacob to testify of His power and love and to teach the world who He is. We have the Bible because the Lord preserved His written word through the Jewish people. The nation of Israel was founded and nurtured of God to bring the Messiah into the world. Jesus, The Word, who became flesh (Psalm 2:7 and John 1:1-14) and dwelt among us was born of a virgin (Isaiah 7:14 and Matt 1:23) and lived a sinless life (1Peter 2:22) and died for the sins of mankind, as prophesied in Isaiah 53 and Daniel 9:26 and Psalms 22:8-18. Jesus rose again from the grave - Psalm 16:10.
Acts 13:33 God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee. Acts 13:34 And as concerning that he raised him up from the dead, now no more to return to corruption, he said on this wise, I will give you the sure mercies of David. Acts 13:35 Wherefore he saith also in another psalm, Thou shalt not suffer thine Holy One to see corruption. Acts 13:36 For David, after he had served his own generation by the will of God, fell on sleep, and was laid unto his fathers, and saw corruption: Acts 13:37 But he, whom God raised again, saw no corruption.
Mary, Jesus' mother, was of the lineage of Abraham, Isaac, Jacob, Judah, David, and Nathan. (Luke 3) Jesus' stepfather, Joseph, was also of the lineage of the Abraham, Isaac, Jacob, Judah, David, and Solomon. (Matthew 1)
The Old Testament pointed to Jesus with prophecies, feasts, types and shadows. The New Testament is a record of Jesus, the Jewish Messiah, and how He fulfilled the prophecies of the Old Testament. It also tells of the future when Jesus will reign forever as KING of KINGS among His people. The New Testament fulfills the Old Testament. Both Old and New are in complete agreement with the other. In order to better understand Daniel, one must read Revelation and vice versa. In order to understand Isaiah 53 and Psalm 22, one must read the account of the crucifixion of Jesus found in the Gospels.
JESUS IS JEWISH
The New Testament is the account of the Messiah. Jesus came from the seed of Abraham and is of seed of David and therefore He is very much Jewish! He has the legal right to rule and reign on the throne of David because He is of the royal lineage of David. Jesus will rule and reign from Jerusalem someday. God keeps His promises and what He promised to Abraham, Isaac, Jacob, Judah, and to David, He will continue to do. God will keep His Word.
Matt 1:21 And she shall bring forth a son, and thou shalt call his name JESUS: for he shall save his people from their sins.
Luke 19:10 For the Son of man is come to seek and to save that which was lost.
Zechariah 12:8 In that day shall the LORD defend the inhabitants of Jerusalem; and he that is feeble among them at that day shall be as David; and the house of David shall be as God, as the angel of the LORD before them. Zechariah 12:9 And it shall come to pass in that day, that I will seek to destroy all the nations that come against Jerusalem. Zechariah 12:10 And I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn.
Revelation 1:7 Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen.