The first mention of the key word "covenant" is in Genesis 6:18, where God promised to establish a covenant with Noah after the Flood. This everlasting covenant was made with all the earth's future populations and is still in effect, symbolized continually by the beautiful rainbow arching through the sky after a rain.
God also made an everlasting covenant with Abraham and Isaac. "And I will establish my covenant between me and thee and thy seed after thee in their generations for an everlasting covenant, to be a God unto thee, and to thy seed after thee. And I will give unto thee, and to thy seed after thee, the land wherein thou art a stranger, all the land of Canaan, for an everlasting possession; and I will be their God" (Genesis 17:7-8). This time, the symbol of God's everlasting covenant between them and their descendents, the people of Israel, was that of circumcision, "a token of the covenant betwixt me and you" (Genesis 17:11).
There is still another everlasting covenant--this one with all the redeemed of all the ages. "I will make an everlasting covenant with them, that I will not turn away from them, to do them good; but I will put my fear in their hearts, that they shall not depart from me" (Jeremiah 32:40). God has made this "new covenant" applicable to all the saved, and this time, the sign of the covenant is nothing less than the precious blood of Christ, shed on our behalf. "Now the God of peace, that brought again from the dead our Lord Jesus, that great shepherd of the sheep, through the blood of the everlasting covenant, Make you perfect in every good work to do his will" (Hebrews 13:20-21). HMM