New Defender's Study Bible Notes
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.