Now the priest of Midian had seven daughters. They came to draw water and filled the troughs to water their father's flock. Then some shepherds arrived and drove them away, but Moses came to their rescue and watered their flock. When they returned to their father Reuel he asked, "Why have you come back so quickly today"? They answered, "An Egyptian rescued us from the shepherds. He even drew water for us and watered the flock." "So where is he?" he asked his daughters. "Why then did you leave the man behind? Invite him to eat dinner." Moses agreed to stay with the man, and he gave his daughter Ẓipporah to Moses (in marriage). (Exodus 2:16-21)
The story of Moses' arrival at the well of Midian, his salvation of the daughters of the priest of Midian and his stay with the priest of Midian is full of lessens concerning the obligation of hakarat hatov, expressing appreciation to one who has been helpful.
According to the simple meaning of the verse, the "Egyptian man" who saved the daughters is Moses. However, Shemot Rabba [1:32] expounds that it refers to the Egyptian whom Moses killed in defense of an Israelite. [above, verses 11-12]:
The daughters of Jethro said to Moses "Thank you for saving us from the shepherds." Moses responded "It is the Egyptian I killed who saved you."
Moses taught the daughters of Jethro that their obligation of hakarat hatov requires them to appreciate the entire situation which brought about their salvation. Had Moses not killed the Egyptian, he would not have had to flee Egypt; had he not fled Egypt, Moses would not have arrived at the well of Midian and he would not have been able to save the daughters of Jethro.
Here we have a lesson about the scope of the obligation of hakarat hatov.
In response to his daughters' informing him that an Egyptian man saved them from the shepherds, Reuel asked "So where is he?", in essence, reprimanding them for failure to fulfill their obligation of hakarat hatov to the person who saved them. Reuel's message is "The man saved you and all you did was say thank you? This is not fulfilment of hakarat hatov."
As part of his expression of hakarat hatov to Moses for having saved his daughters, Jethro gave him Zipporah as a wife and accepted him as a family member. Rashi twice [2:21`4:14] refers to our Sages' tradition [Shemot Rabba 1:33;4:1] that Moses swore to Jethro that he would not move from Midian without his explicit permission. This oath was an expression of Moses' hakarat hatov to his father-in-law, who provided him with a wife and a home.
Following Moses' encounter with God at the burning bush at Mount Horeb, at which God appointed him as the savior of Israel, Moses returned to Midian to ask Jethro's permission to leave Midian and go to Egypt to bring the Israelites out of their bondage. Rabbi BenZion Nesher (head of the rabbinic court of monetary matters in Tel Aviv) presents the following scenario: having returned from Horeb, Moses, said to Jethro "My beloved father-in-law, God has appointed me to lead Israel out of Egypt to freedom, so I ask your permission to leave Midian for Egypt." Jethro answered "I understand the importance of your appointment, however, I need you to stay with me in Midian." Moses repeated his request, saying "Father-in-law, if I do not lead the Israelites to freedom, no one else will be able to" (there is a Midrash which states that only Moses could fulfill the Divine mission). However, Jethro maintained his position, answering "My beloved son-in-law, I understand the reality you describe, but I cannot release you to go down to Egypt." In such a situation, Moses' obligation of hakarat hatov to Jethro would prevail over the salvation of God's Chosen People!

Rabbi Nesher explains that this would have been the necessary and inevitable outcome of this scenario, since Moses' charge was not merely to bring Israel out of Egypt, but to bring them to Torah and teach them Torah. Hakarat hatov is a fundamental concept of Torah, to the point where Naḥmanides defines it as a basic foundation of all Torah. Thus, had Moses begun his career with a violation of his personal obligation of hakarat hatov, he would have disqualified himself from the possibility of fulfilling his prophetic mission. One who violates the obligation of hakarat hatov cannot teach the nation its central importance. It would have been hypocritical for Moses to teach Israel about the centrality of hakarat hatov had he himself not expressed his debt of gratitude to Jethro.
Indeed, there are significant practical lessons from the story of Moses' salvation of the daughters of Jethro and the reactions of the participants in the event. (David Magence)

Shabbat Shalom!
The Va’ad