Matthew Poole and continuators on Joshua 8:3

3 So Joshua arose, and all the people of war, to go up against Ai : and Joshua chose out thirty thousand mighty men of valour, and sent them away by night.

i. e. To consider and conclude about this Expedition of going up against Ai; not as if all the people of war did actually go up, which was both unnecessary and burdensom, and might hinder their following design: but it seems to be resolved by Ioshua and all the Council of War, That the 30000. here following should be selected for the Enterprize. Either, 1. the 30000. now mentioned; Or, 2. part of them; to wit, such as were to lie in wait, as seems most probable both from the next verse, which limits it to those who were to lie in wait, and from v. 9. where what is here mentioned only by anticipation, is actually put in execution; and it is said of them that were sent forth, that they went to lie in ambush, and did so; and these were only 5000. men, as is expressed, v. 12. And the only inconvenience of this Exposition is, That the Pronoun Relative them, is put without, or before its Antecedent, which is left to be gathered out of the following words, which is not unusual in the Hebrew Tongue, as plainly appears from Exod. 14. 19. Numb. 18, 9. and 24. 17. Psal. 87. 1. and 105. 19. and 114. 2. Prov. 7. 8. and 14. 26.