Sforno on Genesis 18:17/ספורנו על בראשית י״ח:י״ז

1ואברהם הולך..וה' אמר. He was constantly busy with good deeds and the fulfillment of G’d’s commandments, such as to see his guests off and accompany them beyond the entrance of his house. This is the meaning behind the words למען אשר יצוה את בניו וג'; if Avraham saw that G’d had revealed His plans for Sodom to him, immediately after he accompanied the angels, he would understand that the performance of such kind deeds resulted in one’s gaining an ever more intimate relationship with G’d. He would be encouraged to instruct his children, etc., to act in this manner [pointing out positive results which would accrue to them as a result. Ed.] This is what is meant in Avot 4,2 שכר מצוה מצוה, “the reward of performing a mitzvah is .that one will be encouraged to perform another mitzvah.

2 המכסה אני, it is appropriate that I do not conceal from Avraham my attribute of goodness; I will inform him that if among all these wicked people in Sodom I find even a quorum of 10 righteous people, this will represent hope that eventually all or most of these people will become penitents. In that event I would bend the scales of justice in favour of the town, giving them an extension of time before destroying them. G’d teaches that He is more interested in the return of sinners to the fold than in administering retribution to them.