Look at the promises, sweet words of God in verses 6-8 that they just couldn't open their hearts to at this time: "Therefore say to the children of Israel: 'I am the Lord; I will bring you out from under the burdens of the Egyptians, I will rescue you from their bondage, and I will redeem you with an outstretched arm and with great judgments. I will take you as My people, and I will be your God. Then you shall know that I am the Lord your God who brings you out from under the burdens of the Egyptians. And I will bring you into the land which I swore to give to Abraham, Isaac, and Jacob; and I will give it to you as a heritage: I am the Lord.'"
Don't be too hard on the children of Israel for not being able to trust and believe at this point. They were under such hardship and stress that most of us have never known. I can't quote him exactly, but Rev. Ron Dunn spoke about trusting God in one of my very favorite sermons of his. The children of Israel eventually had two choices, to trust God and cross the impossible Red Sea (Exodus 14) or to turn around and face the Egyptian army at their heels. God sometimes puts us in situations where we can see that trusting Him is better than the alternative.
Praise You, God, for being my Deliverer.