Although Avram had previously accepted goods from Pharaoh, he refused to accept anything from the evil Sodom. Accepting gifts from the wicked inhibits the recipients from criticizing the giver, and Avram had no intention of ceasing to rebuke Sodom. This thought may be noted from the choice of words in this pasuk. It does not state, “Lest I say … ” which would imply that by accepting these gifts from Sodom, he might forget that all wealth and prosperity comes solely from Hashem. Had this been the reason, he should have similarly refused Pharaoh’s gifts. The pasuk, likewise, does not state, “Lest they say …” (meaning people in general), which would imply that Avram feared that people might consider the inhabitants of Sodom to be kind benefactors. The pasuk states, however, “Lest you say …” (referring to Sodom). If Sodom would bestow wealth on Avram, the inhabitants would consider themselves superior to him, the recipient of their generosity. This feeling of superiority and prestige would have compromised Avram’s ability to chastise them.
We may also derive from here that Avram constantly chided Sodom, constantly urging them to follow his teachings, including the principle of hospitality to wayfarers. It was for this reason that he was so vehement about his refusal. The giver of a gift becomes the teacher. The recipient, in turn, becomes the disciple. Instead of viewing Avram as a mentor, Sodom would mistakenly view itself as the patron. This would prevent the people of Sodom from holding Avram in esteem. By refusing the gifts, Avram was elevated even more in their eyes.