Beshalach: Chapter 27
"And found no water"

"And they marched three days in the wilderness, and found no water;" "water" means the Torah, which had not yet been given to them. Rabbi Elazar says that is true, and that Torah is the Holy One, blessed be He. When they came to the bitter water of Marah, "Hashem showed him a tree;" the "tree" means Torah, and it means the Holy One, blessed be He. It was when they arrived at Marah that they entered fully into the Covenant with God, where "He made for them a statute and an ordinance."