Albert Barnes on Mark 13:37

All, Watch. This command was proper, not only for those who were expecting the calamities that were soon to come upon the Jews, but for all who are soon to die, and to go to the judgment. We know not the time of our death. We know not how soon we shall be called to the judgment. The Son of man may come at any moment, and we should, therefore, be ready. If we are his friends-- if we have been renewed and pardoned--if we have repented of our sins, and have believed on him, and are leading a holy life--we are ready. If not, we are unprepared; and soon, probably while we are not expecting it, the cold hand of death will be laid on us, and we shall be hurried to the place where is weeping, and wailing, and gnashing of teeth. Oh, how important it is to be ready, and to escape the awful sufferings of an ETERNAL HELL!

(w) "Watch" Mk 13:33,35