Adam Clarke on Exodus 14:30

Israel saw the Egyptians dead upon the seashore - By the extraordinary agitation of the waters, no doubt multitudes of the dead Egyptians were cast on the shore, and by their spoils the Israelites were probably furnished with considerable riches, and especially clothing and arms; which latter were essentially necessary to them in their wars with the Amalekites, Basanites, and Amorites, etc., on their way to the promised land. If they did not get their arms in this way, we know not how they got them, as there is not the slightest reason to believe that they brought any with them out of Egypt.