Hebrews 4:1-2 (Go to this verse :: Verse pop-up)
These verses show that Jesus was not the first of God's agents mentioned in the Bible to preach the gospel of the Kingdom of God. The Bible does not name him directly, but Moses is most likely the one who preached to the Israelites. Did he preach it as he and Aaron were preparing the Israelites to leave Egypt? There is a gap in God's revelation here because it is not terribly important who did it.
We can go further back and suppose that Abraham probably heard the gospel from God Himself as he was preparing to leave his homeland for Canaan. Hebrews 11:10 informs us that Abraham "waited for the city which has foundations, whose builder and maker is God." That city is the heavenly Jerusalem that will come down from heaven with the Father when He comes to earth (Revelation 21:1-5). This, too, is an aspect of the gospel of the Kingdom of God.
However, the earliest implication of all appears in Genesis 3:15 within God's pronouncement to Satan of His curse for his involvement in Adam and Eve's sin: "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."
Early in the New Testament, Matthew 3:2 quotes John the Baptist preaching the gospel, saying, "Repent, for the kingdom of heaven is at hand!" However, Jesus certainly gave the most expansive and detailed information regarding the gospel's message. Nobody else even comes close. He also clearly gives the message's title in Mark 1:14-15: "Now after John was put into prison, Jesus came to Galilee, preaching the gospel of the kingdom of God, and saying 'The time is fulfilled and the kingdom of God is at hand. Repent and believe the gospel.'"
John W. Ritenbaugh
Where Is God's True Church Today?