Matthew 24:37

24:37 For just like the days of Noah ¹  were, so the coming of the Son of Man will be.

Matthew 24:42-44

24:42 “Therefore stay alert, because you do not know on what day ²  your Lord will come. 24:43 But understand this: If the owner of the house had known at what time of night the thief ³  was coming, he would have been alert and would not have let his house be broken into. 24:44 Therefore you also must be ready, because the Son of Man will come at an hour when you do not expect him. ⁴ 

Matthew 24:50

24:50 then the master of that slave will come on a day when he does not expect him and at an hour he does not foresee,

¹ sn Like the days of Noah, the time of the flood in Gen 6:5-8:22, the judgment will come as a surprise as people live their day to day lives.

² tc Most later mss (L 0281 Ï lat) have here ὥρᾳ ({wra, “hour”) instead of ἡμέρα (Jemera, “day”). Although the merits of this reading could be argued either way, in light of the overwhelming and diverse early support for ἡμέρᾳ ({א B C D W Δ Θ Ë¹³ 33 892 1424, as well as several versions and fathers}), the more general term is surely correct.

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

⁴ sn Jesus made clear that his coming could not be timed, and suggested it would take some time – so long, in fact, that some will not be looking for him any longer (at an hour when you do not expect him).