Charles Ellicott Commentary Mark 1:15

"and saying, The time is fulfilled, and the kingdom of God is at hand: repent ye, and believe in the gospel." — Mark 1:15 (ASV)

The time is fulfilled.—The words are not found in the parallel passages of the other Gospels, and are interesting as embodying the same thought as St. Paul’s in the fulness of time (Galatians 4:4; Ephesians 1:10). So, too, St. Mark adds believe the gospel to the simple repent of St. Matthew, and gives the kingdom of God instead of the kingdom of heaven.