Charles Ellicott Commentary Mark 13:33

"Take ye heed, watch and pray: for ye know not when the time is." — Mark 13:33 (ASV)

Take ye heed.—Note once more the characteristic iteration of the warning. It would almost seem, from the very different conclusions of the discourse in the three Gospels, as if they had been based up to this point on a common document which then stopped and left them to a greater divergence of memory or tradition. The omission of St. Matthew’s reference to the history of Noah is, perhaps, characteristic of St. Mark’s as a Gentile Gospel.