15:22-27 In the wilderness of Shur the Israelites had no water. At Marah they had water, but it was bitter; so that they could not drink it. God can make bitter to us that from which we promise ourselves most, and often does so in the wilderness of this world, that our wants, and disappointments in the creature, may drive us to the Creator, in whose favour alone true comfort is to be had. In this distress the people fretted, and quarrelled with Moses. Hypocrites may show high affections, and appear earnest in religious exercises, but in the time of temptation they fall away. Even true believers, in seasons of sharp trial, will be tempted to fret, distrust, and murmur. But in every trial we should cast our care upon the Lord, and pour out our hearts before him. We shall then find that a submissive will, a peaceful conscience, and the comforts of the Holy Ghost, will render the bitterest trial tolerable, yea, pleasant. Moses did what the people had neglected to do; he cried unto the Lord. And God provided graciously for them. He directed Moses to a tree which he cast into the waters, when, at once, they were made sweet. Some make this tree typical of the cross of Christ, which sweetens the bitter waters of affliction to all the faithful, and enables them to rejoice in tribulation. But a rebellious Israelite shall fare no better than a rebellious Egyptian. The threatening is implied only, the promise is expressed. God is the great Physician. If we are kept well, it is he that keeps us; if we are made well, it is he that recovers us. He is our life and the length of our days. Let us not forget that we are kept from destruction, and delivered from our enemies, to be the Lord's servants. At Elim they had good water, and enough of it. Though God may, for a time, order his people to encamp by the bitter waters of Marah, that shall not always be their lot. Let us not faint at tribulations.

25. the Lord showed him a tree, which when he had cast into the waters, the waters were made sweet—Some travellers have pronounced this to be the Elvah of the Arabs—a shrub in form and flower resembling our hawthorn; others, the berries of the Ghurkhud—a bush found growing around all brackish fountains. But neither of these shrubs are known by the natives to possess such natural virtues. It is far more likely that God miraculously endowed some tree with the property of purifying the bitter water—a tree employed as the medium, but the sweetening was not dependent upon the nature or quality of the tree, but the power of God (compare Joh 9:6). And hence the "statute and ordinance" that followed, which would have been singularly inopportune if no miracle had been wrought.

and there he proved them—God now brought the Israelites into circumstances which would put their faith and obedience to the test (compare Ge 22:1).