When Gaal saw the people, he said to Zebul, “Behold, people are coming down from the tops of the mountains.”
Zebul said to him, “You are seeing the shadow of the mountains as if they were men.”
“You are seeing the shadow.” The mountains around Mout Gerizim and Mount Ebal cast shadows that move with the sun, and Zebul uses that fact to distract Gaal and give Abimelech more time in his attack.