Sharing the merit of a mitzvah

מה ששאל אברהם אע"ה מהם עצה נראה שהיה רק לטובתם שע"י העצה שיתנו יהי' להם קצת זכות במצות המילה.

That which Avraham Avinu asked them for counsel — it appears that it was only for their benefit, so that through the counsel they would give, they would have some merit (zechus) in the mitzvah of milah.

When Avraham consulted others before performing his bris milah, he did not actually need their advice; he asked only so that by participating in the decision they would share in the zechus of the great mitzvah.

שוב ראיתי שכן הוא בדברי מו"ז ז"ל:

Afterward I saw that so it is in the words of my grandfather, zal.

The Sefas Emes notes that he later found this very explanation in the teachings of his grandfather, the Chiddushei HaRim.

Summary: Avraham Avinu's asking others for counsel before his milah was purely for their sake — so that they could earn a portion of zechus in the mitzvah — an idea the Sefas Emes found confirmed in the words of his grandfather.