Exodus 15: 22-25
22 ¶ So Moses brought Israel from the Red sea, and they went out into the wilderness of Shur; and they went three days in the wilderness, and found no water.
23 And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah.
24 And the people murmured against Moses, saying, What shall we drink?
25 And he cried unto the LORD; and the LORD shewed him a tree, which when he had cast into the waters, the waters were made sweet: there he made for them a statute and an ordinance, and there he proved them,

God brought Israel straightway from the sea to the bitter pool of Marah. Why would God lead those he loved to such a bitter unsatisfying pool? He did not lead them there to drink it, only to taste it. It is only as we taste the bitter waters of Marah that we cry out for the remedy. No sooner had they tasted and cried, God showed them a certain tree. What is this tree? It is the cross of Christ. It is the crucified Redeemer that sweetens all the bitter waters of Shur. The first lesson in the wilderness journey is that the cross is the only sweet thing in the land. It is sufficient, not only to sweeten the bitter pool but every step we take and every circumstance we encounter. In this wilderness journey we are shut up to the grace and mercy of our God. There is nothing in this place to contribute to our preservation. Everything we need our God will supply by his grace and his cross is the supreme manifestation of that. “He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things?” (Romans 8:32) - Darvin Pruitt