Jamieson, Fausset and Brown on Matthew 4:17

17. From that time Jesus began to preach, and to say, Repent; for the kingdom of heaven is at hand--Thus did our Lord not only take up the strain, but give forth the identical summons of His honored forerunner. Our Lord sometimes speaks of the new kingdom as already come--in His own Person and ministry; but the economy of it was only "at hand" until the blood of the cross was shed, and the Spirit on the day of Pentecost opened the fountain for sin and for uncleanness to the world at large.

Calling of Peter and Andrew James and John (Mt 4:18-22).