Exodus 1:10; Exodus 1:11

10 In case of war they might join our enemies in order to fight against us, and might escape from the country. We must find some way to keep them from becoming even more numerous."

11 So the Egyptians put slave drivers over them to crush their spirits with hard labor. The Israelites built the cities of Pithom and Rameses to serve as supply centers for the king.