Question: How does stopping the well of Miriam relate to faith?

Answer: You do mention that the episode describes a lack of faith on the the part of the Jewish people. That is certainly true. The Jewish people are about to enter the land of Israel. This transition was actually quite a momentous one. In the desert, the Jewish people lived a life within a bubble, sheltered by Hashem. All of their needs were taken care of in a supernatural way. It was a very spiritual life. In the land of Israel, in contrast, they would need to live within the confines of nature, and find God through the physical world. This is in fact, God’s plan for the Jewish people, and the ultimate mission of the Jewish people. The bubble of the desert was meant to be temporary, to give the Jewish people the spark they would need to live within the confines of nature and the physical.

The cessation of the well of Miriam was part of this transition from the supernatural to the natural. The Jewish people panicked however. They were so accustomed to the life of the supernatural they did not know how to react when confronted with the world of the natural. Their failing was certainly a lack of faith—that even within the world of the natural, God could, and would provide from them.

Rabbi Yoel Spotts