It is stated in Parashat Va'era (Exodus 7:19): "And the Lord said to Moses, 'Say to Aaron, take your staff and stretch out your hand over the waters of Egypt... and they will become blood; there will be blood throughout the land of Egypt, even in the wooden and stone vessels.'" And in Rashi's commentary: "Say to Aaron – because the Nile protected Moses when he was cast into it, therefore it was not struck by him, neither with blood nor with frogs, but rather by Aaron."

Indeed, our sages have frequently discussed the immense importance of gratitude, and conversely, the severe condemnation of ingratitude. Even here, in the context of the Plagues of Egypt, whose ultimate purpose is to teach us faith, knowledge, and ethics, it is fitting that a lesson regarding the exalted value of gratitude be incorporated.

Accordingly, I would like to express a profound idea based on Rashi's words:

It occurred to me that the Plague of Blood itself, and the matter brought in the Midrash (Shemot Rabbah 9:10), that during the days when this plague prevailed, the Egyptians were compelled to purchase drinking water from the Israelites with full payment. And the Plague of Frogs itself, and what we find related to it in the Gemara (Pesachim 53b), where the frogs sacrificed themselves for the sanctification of God's name in the ovens, from which Chananiah, Mishael, and Azariah learned by analogy to sacrifice themselves for the sanctification of God's name in the fiery furnace – these four aspects, they share a common theme, which is the expression of the concept of gratitude, as follows: