EXOD119 We must be grateful to anyone who has benefited us, even if he did so unintentionally. Rashi cites the Midrash (Shmos Rabbah 9:10) which explains that Aharon rather than Moshe was chosen to initiate the plagues of blood and frogs, because the water had protected Moshe when he was cast into it as an infant. It would therefore not be proper for Moshe to smite the water. Water is an inanimate object which does not have free will. When something floats in water and does not sink, it would not occurred us to give thanks to the water for its buoyancy. Nevertheless, we learn from this verse that if a person drives pleasure from an object, he should show his gratitude by being careful not to cause harm or damage to the object, even though it would not suffer pain. As the Talmud Bava Kama 92b states: "if you drink water from the well, do not throw stones at it." Although this advice is basically meant as a metaphor for people who have given you something, the literal meaning should not be ignored (see Shita Mekubetzes, Bava Kama, ibid.). Since this is true concerning inanimate objects, all the more so must we show gratitude towards people who have shown us kindness. (Rabbi Chayim Shmuelevitz). Rabbi Yechezkail Sarna, Rosh Yeshiva of Chevron, wrote that the obligation to show gratitude for a well applies especially to a spiritual well. If you have studied Torah under a certain teacher or if you have stayed in a certain yeshiva, appreciate what you have gained. Be careful not to throw verbal stones at the spiritual wells from which you have drunk. (Daliyos Yechezkail, vol. 2, p. 305).