'Unexpectedly' in the Bible

Gideon went up by the route of those who lived in tents to the east of Nobah and Jogbehah, and he attacked their camp when the camp was unsuspecting.

After an alliance is made with him he will work deceitfully, and he will go up and gain power with a small force of people.

[stay alert,] in case he should come suddenly and unexpectedly and find you asleep and unprepared.

For you yourselves know perfectly well that the day of the [return of the] Lord is coming just as a thief [comes unexpectedly and suddenly] in the night.