Adam Clarke on Joshua 2:5

When it was dark - So it appears that it was after night that the king of Jericho sent to Rahab, ordering her to produce the persons who lodged with her. The season itself was friendly to the whole plot: had these transactions taken place in daylight, it is scarcely possible that the spies could have escaped. But this is no excuse for the woman's prevarication, for God could have saved his messengers independently of her falsity. God never says to any, Do evil that good may come of it. See at the end of the chapter, Jos 2:24 (note).