In the verse, “for you have passed by your servant,” RASHI interpreted, “for this I ask of you, since you passed by me, to honor me.” We should understand the words “to honor me.” Abraham said, “And I am dust and ashes,” and he said, “since you passed by me, to honor me.”
We should understand that since he feared that they would not want to eat at his place because of shame, he said, “to honor me,” meaning by this you will honor me, namely that they would be the givers and not the receivers. By this, he removed from them the shame, called “bread of shame.”