30 Thus the Lord saved Israel that day out of the hand of the Egyptians; and Israel saw the Egyptians dead upon the sea shore. 31 And Israel saw that great work which the Lord did upon the Egyptians: and the people feared the Lord, and believed the Lord, and his servant Moses.
Today’s verses find the Israelites safe on the other side of the sea, and the Egyptians dead, their bodies strewn across the shore. This image of the Israelites safe above the waterline and the Egyptians having been drowned in its depths has a strong similarly to that of Noah and his family safe above the water in the ark while all the world was smothered down below. The Israelites and the Egyptians had just carried out a sort of reenactment of that scene, reinforcing its lessons. Lessons that too much of the world, especially Egypt, had forgotten.
I also want to note how verse 31 stresses the faith and trust that the people had in the Lord and Moses at this moment. Just a few verses before we had heard of their despair and doubt when the Egyptian horde came charging into view, but now they have a moment of perfect belief, trusting not only in the Lord, but also in His prophet and mouthpiece, Moses.
I believe that sometimes we are saved by God, not because of who we are, but because of what He knows we can become. Pharaoh had proven that in spite of miracles he would still not believe, and so he had been destroyed. The Israelites, though they had disbelieved before the miracle, would believe after it, and so they were preserved. We will see how the Lord would continue to test the Israelites with future hardships, and they would not see the Promised Land until they showed that they were ready to start believing before the miracle.