3 The day of the Lord is the period of time in the future when the Lord will intervene in the events of this earth to consummate his redemption and his judgment (Isa 2:11–12; 13:6–13; Ezek 30:3; Joel 1:15; 2:32; 3:18; Amos 5:18–20; Obad 15–17; Zeph 1:7–18; 2:2–3; Zech 14:1, 13, 20–21; Mal 4:1, 5; 1 Cor 1:8; 5:5; 2 Cor 1:14; 2 Thess 2:2; 2 Pet 3:10). It includes both blessings and curses, though the latter is emphasized here.
4 Jesus used a thief coming at night as an illustration of the unexpected and hostile nature of the coming of God’s judgment in the future. This is repeated in various ways in v. 4; 2 Pet 3:10; Rev 3:3; 16:15.

In other versions

For you yourselves are fully aware that the day of the Lord will come like a thief in the night.

for you know very well that the day of the Lord will come like a thief in the night.

For you yourselves know very well that the day of the Lord will come just like a thief in the night.

For you know quite well that the day of the Lord’s return will come unexpectedly, like a thief in the night.

for you yourselves well know that the day of the Lord is coming in the same way as a thief in the night.

For yourselves know perfectly that the day of the Lord so cometh as a thief in the night.

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