Then Moses made Israel set out from the Red Sea, and they went into the wilderness of Shur. They went three days in the wilderness and found no water. When they came to Marah, they could not drink the water of Marah because it was bitter; therefore it was named Marah. And the people grumbled against Moses, saying, "What shall we drink?" And he cried to the LORD, and the LORD showed him a log, and he threw it into the water, and the water became sweet. There the LORD made for them a statute and a rule, and there he tested them, saying, "If you will diligently listen to the voice of the LORD your God, and do that which is right in his eyes, and give ear to his commandments and keep all his statutes, I will put none of the diseases on you that I put on the Egyptians, for I am the LORD, your healer." Then they came to Elim, where there were twelve springs of water and seventy palm trees, and they encamped there by the water.
Exodus 15:22-27
The bitter waters of Marah were encountered almost as soon as Israel's pilgrimage began, and this is surely meant to teach us that the spiritual life of God's people is never likely, nor meant, to be an easy one. One thinks of Bunyan's true insight in making Christian in the Pilgrim's Progress encounter the Hill Difficulty directly he moved on from the experience of pardon and rebirth at the Cross. The entire testimony of Scripture is that the Christian way is one that lays discipline and testing and trial on those who engage in it. It is true that there are always some who wish for an easy life, and who allow this wish to dominate everything else in life. This is how it was with some in Israel, and explains the constant spirit of murmuring among them which eventually led them, at the crucial moment on the borders of the Promised Land, to turn back when they might have entered in, and when they were well able to do so. This is a deadly dangerous attitude. To be unwilling to face the discipline of difficulty and hard times is to run contrary to the real essence of life. All great advances and discoveries in human culture, science or medicine are made in the face of the greatest difficulties and often after many failures, disappointments and discouragements. Why should it be thought that the spiritual life will be different, offering as it does the greatest discovery and prize of all? A spiritual life that costs nothing is worth nothing and will get us nowhere. (The New Testament parallel is found in the disciples' unwillingness to receive Jesus' teaching about taking up the Cross to follow Him. They wanted an easier way).