Num 13:31
31 But the others said, "We can't attack those people; they're way stronger than we are."

God had told then that He would fight for them and that He was giving the land to them but they only relied on what they could see and think but what they could see and think in Egypt was that they had to be slaves and God freed them from that. We have the same problem of only relying on what we can see and think…