In Exodus, God shows off.
He is displaying his power and getting himself glory; raining down the plagues that will break Pharoah's back, foreshadowing Christ in the Passover Lamb, manifesting all over the place his infinite power, wisdom and glory. It's a tremendous display!
All this that they may "know that I am the LORD" (14:4).
As God is revealing himself, he is establishing the national identity of his covenant people, Israel. He is showing them what kind of God has called them to be his. The LORD makes himself known to Israel as the God who can meet their every need; the God they can TRUST.
The climax of this comes at the Red Sea. Mighty waters in front of them; a hardened, outraged king and his army behind them. After all the plagues and all of God's displayed power, the people complain. "Is it because there are no graves in Egypt that you have taken us away to die in the wilderness?" (14:11, ESV). Moses' answer reveals that he trusts God: "Fear not, stand firm, and see the salvation of the LORD, which he will work for you today. For the Egyptians whom you see today, you shall never see again" (v13). You know what follows. He raises his staff and his hand over the Red Sea, and God PARTS IT. God told the people to "go forward..." (v15) into the Sea. And with his power he parted the waters and provided for his covenant people a great salvation from their enemies.
Hallelujah! The next thing we see is the hundreds of thousands of Israelites partying on the other side of the sea: Moses leads them in a song of praise to God; Miriam leads the women in dances with tambourines. They are camped out on the beach singing and dancing and making music to God while the dead bodies of their enemies wash up to the shore (14:30).
But the party stops when they move on into the wilderness, headed for the promised land, and can't find any water! Oh, how soon we forget what our awesome God is capable of doing! How soon we go from praise to pathetic complaining and whining. God was able to PART the mighty waters... Is he also not able to PRODUCE drinking water? God was able to eliminate their enemies; is he also not able to provide for their needs?
This is US, too much of the time. God demonstrated his love by giving us his Son at the cross to save us from judgment and give us eternal life. Day after day he wakes us up to blessings beyond number. Air to breathe. Food to eat. Brothers and sisters in Christ. His wrath removed in Christ. Eternal love poured out. Glimpses of his glory through grace! He shows us his ability to provide and his power to set us free. But then we come to the bitter waters of Marah, and we forget.
God changed the bitter waters and made them sweet (15:25). Then he led the multitude to an oasis in the wilderness, with twelve springs of water and seventy palm trees, "and they encampted there by the water" (27).
Praise God! Let us remember what he has done for us! And let us not be quick to forget the greatness of our God when the water runs out. In times of testing, look to the Lord; TRUST in the Lord. Give him the glory! Salvation is coming...