Adam Clarke on Matthew 4:17

Jesus began to preach, and to say, Repent - See on Mat 3:1, Mat 3:2 (note). Every preacher commissioned by God to proclaim salvation to a lost world, begins his work with preaching the doctrine of repentance. This was the case with all the prophets, John the Baptist, Jesus Christ, all the apostles, and all their genuine successors in the Christian ministry. The reasons are evident in the notes already referred to; and for the explanation of the word κηρυσσειν, preaching or proclaiming as a herald, see at the end of chap. 3 (note).