Matthew 24:43

24:43 But understand this: If the owner of the house had known at what time of night the thief ¹  was coming, he would have been alert and would not have let his house be broken into.

Luke 12:38

12:38 Even if he comes in the second or third watch of the night ²  and finds them alert, ³  blessed are those slaves! ⁴ 

[24:43]  ¹ sn On Jesus pictured as a returning thief, see 1 Thess 5:2, 4; 2 Pet 3:10; Rev 3:3; 16:15.

[12:38]  ² sn The second or third watch of the night would be between 9 p.m. and 3 a.m. on a Roman schedule and 10 p.m. to 6 a.m. on a Jewish schedule. Luke uses the four-watch schedule of the Romans in Acts 12:4, so that is more probable here. Regardless of the precise times of the watches, however, it is clear that the late-night watches when a person is least alert are in view here.

[12:38]  ³ tn Grk “finds (them) thus”; but this has been clarified in the translation by referring to the status (“alert”) mentioned in v. 37.

[12:38]  ⁴ tn Grk “blessed are they”; the referent (the watchful slaves, v. 37) has been specified in the translation for clarity.