He may find you
When he comes
μὴ ἐλθὼν ἐξαίφνης εὕρῃ ὑμᾶς καθεύδοντας.
This saying is unique to Mark. Jesus warned that the land owner might find them asleep (εὕρῃ ὑμᾶς καθεύδοντας), if he returned or came back suddenly (μὴ ἐλθὼν ἐξαίφνης). You had to be vigilant all the time, including night time.