‘ And when Gaal saw the people, he said to Zebul, “Look, there are people coming down from the mountain heights.” And Zebul said to him, “You are seeing the shadow of the mountains, as if they were men.” ' '
Gaal was accompanied by Zebul, probably not suspecting that he knew of the proposed insurrection, (he had not been at the feast), and as he looked towards the mountains he thought he spotted a company of men coming down towards the city. So he pointed them out to Zebul to ask him what he thought it was. Shechem was situated between two mountains, Ebal and Gerizim, which towered over it.
“And Zebul said to him, “You are seeing the shadow of the mountains, as if they were men.” ” Zebul had his wits about him and replied calmly that Gaal was deceiving himself. What he was actually seeing was moving shadows on the mountains which simply gave the appearance of being men. All this gave Abimelech time to get nearer.