15:1 sang Moses. This is the first recorded “song” in Scripture, and is probably the “song of Moses” referred to in Revelation 15:3, where Moses’ song is combined with the “song of the Lamb” at the glassy sea in the heavenly temple. The latter is the final “song” in the Bible, and the theme of both the first and last songs, is the ultimate fulfillment of God’s purpose in creation. This victorious song of Moses after crossing the sea actually seems to be reflected in a series of inscriptions on cliffs in the Sinai peninsula discovered in the nineteenth century, either made by some of the Israelites at the time or possibly by later Israelite pilgrims desiring to memorialize the great event.

15:8 congealed. That is, “coagulated,” like gelatin.

15:20 Miriam the prophetess. This is the first reference to Moses’ older sister since the time she watched him in the ark of bulrushes where his mother had hid him from Pharaoh when he was a baby (Exodus 2:4,7). This is also the only reference to Miriam as a prophetess.

15:24 the people murmured. Note God’s responses to the murmurings (complainings) of Israel, acting for a while in grace and patience, but eventually acting in judgment. He first provided pure water (Exodus 15:25), next He provided food (Exodus 16:2,7,8,9,12), and then a continuous water supply (Exodus 17:3). But eventually God sent them into exile in the wilderness (Numbers 14:2,27,29,36) and even put many to death (Numbers 16:11,41). Finally, their murmurings ceased after the miracle of the budding of Aaron’s rod, which was a symbol of the resurrection (Numbers 17:5,10). God’s attitude toward murmuring on the part of believers today is indicated in I Corinthians 10:10 and Philippians 2:14.

15:25 shewed him a tree. The miracle here may be simply that of revealing to Moses a tree whose bark or leaves had the ability to react chemically with the noxious waters of Marah (meaning “bitter”) to make them potable. This possibility cannot be pursued in the present absence of knowledge concerning the nature of either the waters or the tree. Of course, the phenomenon could also have been an actual physical miracle. In any case, the complaints of the people gave God an occasion again to show Himself able to meet their needs but also to urge them henceforth to be obedient and believing people.

15:26 none of these diseases. The Israelites were familiar with “the evil diseases of Egypt” (Deuteronomy 7:15), but obedience to God’s laws, which included numerous laws of sanitation not understood until modern times, would keep them in good health.