John Calvin Commentary Joshua 10:8

"And Jehovah said unto Joshua, Fear them not: for I have delivered them into thy hands; there shall not a man of them stand before thee." — Joshua 10:8 (ASV)

And the Lord discomfited them, etc. It is uncertain whether the Lord anticipated the movement and armed Joshua by his oracle, drawing him out from Gilgal before he had taken any step, or whether he only confirmed him after he had made his preparations for setting out. It seems to me more likely that Joshua did not rush out as soon as he was asked without consulting God, but eventually, after being informed of his will, took up arms boldly and speedily. As he had recently been disciplined for excessive trustfulness, it is at least a probable conjecture that in this case of difficulty, he attempted nothing unless he had a divine command. The Lord, therefore, had concern for the miserable Gibeonites when he did not allow them to remain without the help of his people.

Joshua is made confident of victory so that he may help them; for God motivates us more strongly to carry out our duty by promising than by ordering. What is here promised to one belongs to all, but for the sake of honoring Joshua, it is entrusted specifically to him so that he may afterwards be the one to convey it to his army. For God does not speak from heaven to everyone without distinction, but bestows the honor only on excellent servants and chosen prophets.

It is also noteworthy that Joshua did not abuse the divine promise by making it an excuse for laziness, but felt all the more intensely spurred on after he was assured of a successful outcome. Many, while they showily express their faith, become lazy and idle from a false sense of security. Joshua hears that victory is in his hand, and to gain it, he runs swiftly to battle. For he knew that the successful outcome was revealed, not for the purpose of slowing him down or making him more careless, but of making him strive with greater zeal. Thus, he took the enemy by surprise.