In Romans 15, Paul tells the Gentile Christians that they are debtors to our Jewish brethren (Jews who believe in Jesus the Messiah) because we have become partakers of their spiritual things.
For if the Gentiles have been made partakers of their spiritual things, their duty is also to minister unto them in carnal things. ~ See Romans 15:27
Being indebted is a reference to love and gratitude.
The salvation that God has provided through our Lord Jesus Christ has come through his covenant with Abraham and Abraham’s descendants. In scripture, the Messiahship of Jesus cannot be separated from his physical lineage to Abraham. Matthew gives us the genealogy of Jesus for this purpose and in Romans Paul links God’s promise in the gospel to Jesus as the seed of David.
Paul, a servant of Jesus Christ, called to be an apostle, separated unto the gospel of God, (Which he had promised afore by his prophets in the holy scriptures,) Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh; And declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead… ~ Romans 1:1-4
In Hebrews 2, the author of Hebrews declares concerning Jesus’s humanity: For verily he took not on him the nature of angels; but he took on him the seed of Abraham. ~ Hebrews 2:16
In the book of the Revelation, the heavenly messenger said to John, Weep not: behold, the Lion of the tribe of Judah, the Root of David, hath prevailed to open the book, and to loose the seven seals thereof. ~ See Revelation 5:5. And at the close of the book of the Revelation, Jesus himself declares, “I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, and the bright and morning star.” ~ Revelation 22:16
In Acts 7, Stephen preached the gospel before the Sanhedrin declaring how God fulfilled his promises through the death and resurrection of Jesus within the context of the narrative of the story of Israel. In fact, every gospel sermon in the book of Acts is wrapped in the story of Israel.
When Jesus said to the Samaritan woman, “salvation is of the Jews”, it was within the context of seeking and worshipping the one true God. The one true God chose Abraham and his descendants to be his people forever and to make his name glorious and throughout the earth. The salvation that God has provided through his Son, Jesus Christ, cannot be separated from God’s call of Abraham and the story of Israel, to whom pertaineth the adoption, and the glory, and the covenants, and the giving of the law, and the service of God, and the promises; Whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen. ~ Romans 9:4-5
The mystery of Christ came through Abraham’s family and this is how salvation is of the Jews, Gentiles who are saved are grafted into Abraham’s family through Jesus the Messiah, and in this manner we are indebted to Israel. Whenever anyone separates salvation in Jesus from the story of Israel a false gospel is formulated. The gospel by which we are saved is forever united with God’s covenant to Israel which began with Abraham, for he established a testimony in Jacob ~ Psalm 78:5.
The God who has saved the Gentiles is the God of Israel, and for that we are to be indebted with gratitude and love.
In closing consider the words of Zacharias who prophesied by the Holy Spirit:
And his father Zacharias was filled with the Holy Ghost, and prophesied, saying, Blessed be the Lord God of Israel; for he hath visited and redeemed his people, And hath raised up an horn of salvation for us in the house of his servant David; As he spake by the mouth of his holy prophets, which have been since the world began: That we should be saved from our enemies, and from the hand of all that hate us; To perform the mercy promised to our fathers, and to remember his holy covenant; The oath which he sware to our father Abraham, That he would grant unto us, that we being delivered out of the hand of our enemies might serve him without fear, In holiness and righteousness before him, all the days of our life. And thou, child, shalt be called the prophet of the Highest: for thou shalt go before the face of the Lord to prepare his ways; To give knowledge of salvation unto his people by the remission of their sins, Through the tender mercy of our God; whereby the dayspring from on high hath visited us, To give light to them that sit in darkness and in the shadow of death, to guide our feet into the way of peace. ~ Luke 1:67-79
The salvation which we have in Jesus Christ, has come through God’s covenant with the father of our faith, Abraham.