Judges 20:29, 30: The Third Battle at Gibeah: Setting the Ambush
Verse 29: And Israel (so Josh. 8:4) set liers in wait round about Gibeah.
[And they set ambushes] The promise of God notwithstanding, tomorrow I will deliver them, etc. This matter teaches that human industry ought not to cease, even when we have an infallible Divine promise: for the promise of God does not exclude the industry of man, but rather confirms, and guides to a happy outcome (Estius).
Israel set liers in wait: Though they were assured of the success by a particular and absolute promise, yet they do not neglect the use of means; as well knowing that the certainty of God’s purposes or promises doth not excuse, but rather require man’s diligent use of all fit means for the accomplishment of them. Round about Gibeah, that is, on several sides of it, as may be gathered from the following verses.
Verse 30: And the children of Israel went up against the children of Benjamin on the third day, and put themselves in array against Gibeah, as at other times.
The children of Israel, that is, a considerable part of them, who were ordered to give the first onset, and then to counterfeit flight, to draw the Benjamites forth of their strong hold. See verse 32. On the third day, to wit, after the second battle; for the first day after it they spent in perplexing thoughts, and going up to the house of the Lord; the second, in fasting and prayer there; and this third, in the fight. Or this is so called with respect unto the two several foregoing days of battle, and so this was the third day of battle.
 Hebrew: וַיָּ֤שֶׂם יִשְׂרָאֵל֙ אֹֽרְבִ֔ים אֶל־הַגִּבְעָ֖ה סָבִֽיב׃
 Hebrew: וַיַּעֲל֧וּ בְנֵֽי־יִשְׂרָאֵ֛ל אֶל־בְּנֵ֥י בִנְיָמִ֖ן בַּיּ֣וֹם הַשְּׁלִישִׁ֑י וַיַּעַרְכ֥וּ אֶל־הַגִּבְעָ֖ה כְּפַ֥עַם בְּפָֽעַם׃