John Gill Commentary Joshua 10:17

"And it was told Joshua, saying, The five kings are found, hidden in the cave at Makkedah." — Joshua 10:17 (ASV)

And it was told Joshua
Either by some of his own people, or by some of the inhabitants of the land in his interest, who had observed it:

saying, the five kings are found hid in a cave at Makkedah :
this seems to make it appear that they were others, and not Joshua's soldiers, that found them; for had they, no doubt they would have seized them, and brought them before him, or slain them, unless they chose first to know his will concerning them, next expressed.