Luke 12:38

ἐν τῇ δευτέρᾳ, κἂν ἐν τῇ τρίτῃ φυλακῇ ἔλθῃ. It is not clear, nor very important, whether St Luke here alludes to the three watches of the Jews and Greeks (Lamentations 2:19; Judges 7:19; Exodus 14:24) or to the four of the Romans (Jerome, Ep. CXL.). But it is very important to observe that often as our Lord bade His disciples to be ready for His return, He as often indicates that His return might be long delayed, Matthew 25:5-19. He always implied that He should come suddenly (Luke 21:34-36; 1 Thessalonians 5:2-6; Revelation 3:3), but not necessarily soon, Luke 12:46; 2 Peter 3:8-9. “The Parousia does not come so quickly as impatience, nor yet so late as carelessness, supposes.” Van Oosterzee.