Lech L'cha: not leaving room for an alternative explanation

Parshat Lech L'Cha

After Avram was victorious in his battle and freed Lot and others from S'dom, we find the king of S'dom telling Avram to return the people but keep the money. In 14:23 Avram rejects that request by saying, "אִם-מִחוּט וְעַד שְׂרוֹךְ-נַעַל, וְאִם-אֶקַּח מִכָּל-אֲשֶׁר-לָךְ; וְלֹא תֹאמַר, אֲנִי הֶעֱשַׁרְתִּי אֶת-אַבְרָם." I will not take anything, from a thread to a shoelace of what is yours, so you should not say I made Avram wealthy.

Rashi adds that the reason Avram was insistent on this was because Hashem had promised Avram great wealth, so it must come from Hashem and not from the king of S'dom.

Maybe this was how Hashem planned to make Avram wealthy? Did Avram expect a pot of gold to fall from heavan? Clearly Hashem woudl find a natural way to make Avram wealthy, and maybe this incident with the king of S'dom was that method? How could Avram reject this request based on the above logic?

A person has to be acreful to not just do the right thing but also to make the right impression.

For Avram to accede to the request of the king of S'dom, that would leave open in people's minds the possibility that it came from the gemerosity of S'dom rather than from Hashem and His blessing. Sure, maybe this was how Hashem wanted to give it to Avram, but Avram could not allow anyone to think that maybe it was not from hashem but from S'dom. By accepting the wealth from the king in this fashion, it would not close the door 100% but would leave rooom for an alternate explanation.

Avram was all abotu kiddush Hashem. There is no way he could accept that wealth and have people possibly think that he was made wealthy by S'dom rather than by Hashem.