The Covenant of Grace is the Gospel by another name. Immediately after Adam had broken the Covenant of Works (by instead covenanting with Satan and eating the forbidden fruit) God began to reveal the Covenant of Grace. This He did by giving the Gospel promise, cursing the serpent Satan and also saying to him: “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” Genesis 3:15.
As per the Gospel promise, in time the Seed of the Woman inflicted a fatal or head wound when He bruised or crushed the serpent’s head at Golgotha, the Place of the Skull – while having His own heel as opposed to His head wounded, ie, receiving a non-fatal or temporarily fatal wound.
Christ is “the Lamb slain from the foundation of the world” (Rev. 13:8b). Therefore it was actually God who sacrificed His own Son (as pre-figured by Abraham’s almost sacrifice of his (only) son Isaac, Gen. 22). The promised Seed, ie, Christ was to come from the loins of the aged Abraham and his (barren) wife, Sarah (Gen. 18).
The Gospel promise was made earlier to Abraham where God says, “In you all the families of the earth shall be blessed” Genesis 12:3b. The blessing flows through Christ, the Word, who is the promised Seed, Gal. 3:16. Also, “The Word of the LORD came to Abram in a vision, saying, ‘Do not be afraid, Abram. I am your shield, your exceedingly great reward” Genesis 15:1. And, as Abraham’s shield and exceedingly great reward says, “Your father Abraham rejoice to see My day, and he saw it and was glad” John 8:56. The outpouring of the Holy Spirit on all peoples is toward the fulfilment of all the families on earth being blessed…
Abraham seemed very much like a man who had heard Good News, ie, the Gospel. “And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the Gospel to Abraham beforehand saying, ‘In you all the nations of the earth shall be blessed’” Galatians 3:8.
By the time of Moses the people of God were seeing the Gospel depicted in the Ceremonial Law, ie, the sacrificial system, the Ark of the Covenant, the Tabernacle and then the Temple etc. Jesus Christ is the fulfilment of all these. These all were types. He is the great antitype. Thus the Old Testament is full of the Gospel!
The Covenant of Grace was differently administered in the Old Testament. Thus Circumcision and Passover were pictures of the Gospel, the Good News. These blood sacraments became the unbloody New Testament sacraments of Baptism and the Lord’s Supper respectively. Circumcision and Baptism have the same Covenantal meaning, (ie, regeneration, the removal of sin, cleansing etc.) And Passover and the Lord’s Supper both speak of “the Lamb that takes away the sin of the world.”
The saints in both the Old and the New Testaments looked to the Messiah, the Christ, the One who would be Covenantally anointed in His baptism with water and with the Holy Spirit (John 1 etc.), the One who, at His last Covenant Meal transformed the Passover into the Lord’s Supper (Luke 22:19-20).
Thus God’s eternal Covenant was differently administered at different periods throughout the Old Testament, but all of it spoke of Christ, the Seed of the Woman.
This is what we call the Covenant of Grace. It is the promise of God in which He says that He shall be our God and that we shall be His people, Immanuel (Lev. 26:12). In our own day the shorthand way of speaking of the Covenant of Grace is to use the word “Gospel” or “Good News.”
The Seed of the Woman was as it were conceived in Genesis 3:15 and was born in the New Testament. However, this was no unplanned pregnancy, but had been planned from eternity as per God’s eternal Covenant. He is our God and we are His people!