Jamieson, Fausset and Brown on Genesis 18:33

33. the Lord ... left communing ... and Abraham returned unto his place--Why did Abraham cease to carry his intercessions farther? Either because he fondly thought that he was now sure of the cities being preserved (Lu 13:9), or because the Lord restrained his mind from further intercession (Jr 7:16; 11:14). But there were not ten "righteous persons." There was only one, and he might without injustice have perished in the general overthrow (Ec 9:2). But a difference is sometimes made, and on this occasion the grace of God was manifested in a signal manner for the sake of Abraham. What a blessing to be connected with a saint of God!