The first messianic prophecy about Jesus occurs in the third chapter of Genesis, immediately after Adam and Eve have fallen into sin by eating the forbidden fruit in the Garden of Eden. As God is administering His judgement for their sin He is unveiling His promise of redemption.
Genesis 3:15 – And I will put enmity between you and the woman, and between your seed and her seed; He shall bruise your head, and you shall bruise His heel.
God is cursing the serpent (Satan) who caused Adam to sin against God while at the same time announcing the gospel and the Redeemer to come. The offspring or seed of the woman referred to here is Jesus Christ – He is to be born of a woman (Mary), but not by man (Joseph), but sired by the Holy Spirit. Satan will bruise the heel of Jesus by making Him suffer and literally nailing His heel to the cross. Jesus will crush the head of Satan by His triumph over death and the redemption of believers through his sacrificial death on the cross and His resurrection. Jesus would defeat death and reclaim what Adam had lost.
In Genesis we also learn of the Abrahamic covenant whereby God promises Abraham that through him all the nations of the earth will be blessed. This is the gospel message given to Abraham. Jesus is that Messiah, a descendant of Abraham, who will bless all nations by bringing redemption and salvation to fallen mankind by His sacrificial death. All the books of the Old Testament after Genesis are a continuation of this salvation history culminating in the birth, crucifixion, death and resurrection of Jesus Christ. The coming of Jesus to save mankind is the theme of the entire Bible. Without Jesus the Bible doesn’t make sense.