Charles Ellicott Commentary Joshua 8:18

"And Jehovah said unto Joshua, Stretch out the javelin that is in thy hand toward Ai; for I will give it into thy hand. And Joshua stretched out the javelin that was in his hand toward the city." — Joshua 8:18 (ASV)

And the Lord said unto Joshua, Stretch out the spear. —In the capture of Ai, as in that of Jericho, each stage of the process must be ordered by the Lord. In the former case the hand of Jehovah alone does the work. The ark is carried around the walls until they fall down before it. Against Ai, the hand of Israel is employed, and first of all in Israel the hand of Joshua. He seems to have stretched it out, with the light spear or javelin which he carried, somewhat as Moses stretched out the rod of God over the contending armies of Amalek and Israel, until the enemy was defeated with the edge of the sword.