"The hero as confidant of God: The portrait of Abraham as hero is a dynamic one. With each successive episode, something new is added to the portrait. Often we see Abraham in a new role that advances the portrait over what has preceded. In [Genesis 18], God takes Abraham into his confidence in a way that we had not seen before."

Note on Gen. 18 in The Literary Study Bible

"For I have chosen him, that he may command his children and his household after him to keep the way of the Lord by doing righteousness and justice, so that the Lord may bring to Abraham what he had promised him."

Genesis 18:19, ESV