“And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.”
King James Version (KJV)
3:29 If ye are Christ's - That is, believers in him.
Ga 3:29 If ye [be] Christ's, then are ye Abraham's seed, and heirs according to the promise. As Christ is the seed of Abraham, all in Christ become the spiritual seed of Abraham, and hence heirs of the promise to Abraham's seed.