26 For Joshua drew not his hand back, wherewith he stretched out the spear, until he had utterly destroyed all the inhabitants of Ai.
English Standard Version
26 But Joshua did not draw back his hand with which he stretched out the javelin until he had devoted all the inhabitants of Ai to destruction.That is, set apart (devoted) as an offering to the Lord (for destruction)
26 Joshua didn't lower his outstretched javelin until the sacred destruction of Ai and all its people was completed.
New King James Version
26 For Joshua did not draw back his hand, with which he stretched out the spear, until he had utterly destroyed all the inhabitants of Ai.
New Living Translation
26 For Joshua kept holding out his spear until everyone who had lived in Ai was completely destroyed.
God, the righteous Judge, had sentenced the Canaanites for their wickedness; the Israelites only executed his doom. None of their conduct can be drawn into an example for others. Especial reason no doubt there was for this severity to the king of Ai; it is likely he had been notoriously wicked and vile, and a blasphemer of the God of Israel.