A.T. Robertson Commentary Matthew 24:44

"Therefore be ye also ready; for in an hour that ye think not the Son of man cometh." — Matthew 24:44 (ASV)

That ye think not (η ου δοκειτε ωρα). It is useless to set the day and hour for Christ's coming. It is folly to neglect it. This figure of the thief will be used also by Paul concerning the unexpectedness of Christ's second coming (1 Thessalonians 5:2). See also Mt 24:50 for the unexpectedness of the coming with punishment for the evil servant.