The burden of their slavery had taken over their believer. The vision had gotten buried under circumstances. Hopelessness had swallowed up hope. Their ancestor Abraham had received the word of the slavery and the deliverance. That story had been handed down through time to the people that Moses was talking to. Instead of looking at the promise of God, they had successfully been taken over by the cares of this world. Their slavery had been bad enough before, but just before this in scripture, the Hebrew slaves had been told to not only make as many bricks as they did before, but now they had to get the straw themselves also. What we need to take away from this:
Sometimes things get worse before they get better.
God's promises are true.
Believe everything that God tells you.
I think that if the children of Israel would have listened to Moses and just packed up and left, the Lord would have protected them and they could have walked right out---by faith. But there are a lot of lessons about human nature that we would not have in the bible if they had just believed the Word and acted on it. This blog could get really long if I chase that down.---Be Blessed---c