God selected the Patriarch Abraham with this plan of a Saviour and Salvation from sin in mind and made certain promises to him and to his seed. "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" (Genesis 12:3). The fullest and most comprehensive sense in which we are to understand the word "seed" is the Messiah, the Christ that God planned to send into the world to provide salvation by dying for our sins. The remainder of the verse quoted at the beginning tells us, "He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ" (Galatians 3:16b). Hebrews 1:2 tells us that He is the heir of all things.
God's promise to Abraham lays the foundation for the Good News of salvation through Jesus Christ, and the eternal blessings of forgiveness and everlasting life depend entirely on our relationship to Him. We receive the blessings of Abrahamic promise through faith in Christ alone. "For all the promises of God in him are yea, and in him Amen" (II Corinthians 1:20a). Those who believe in Jesus Christ are also spoken of as the seed of Abraham. "And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise" (Galatians 3:29).
There is also a sense in which the Bible speaks of Israel as Abraham's seed. God yet has a plan for that nation through the Messiah, as spoken of in Bible prophecy. The promise of God to bless them that bless Abraham's seed has been proved in history by the smile of providence upon the nations that sympathize with Israel despite the prevalence of world antisemitism.