Ten years before the events of Genesis 15, Abram at 76 submitted himself to God’s judgment for the sake of peace, and let Lot choose what physically looked to be the best territory. On Lot’s part, here is another decision driven by the mind of men based on what is seen that did not work out very well either.
Now with this let us get back to Abraham. In chapter 13 we saw Abram taking a step in faith of self-sacrifice for the sake of peace, while literally putting his own destiny into God’s hands when separating from Lot. And within God’s favor he ended up in the Land of Promise and his own home base of operation for the rest of his life, “by the Terebinth trees of Mamre, which are in Hebron,” as we read in Genesis 13:18. This was 23 years before the events of Genesis 18 and his interaction with the Lord and two angels, and the first time the English word for favor is used in the Bible.
Over this 23-year period of time we see he had been growing in grace and knowledge, while maintaining His humble attitude. He was actively involved in a relationship with God, who was showing His friend that his own solutions to problems were not the answer. He was continuing to earn God’s favor through humble submission and trembling at God’s Word—building layers of mutual trust as he was trusting the Lord with all his heart and not leaning on his own understanding of things, just as it says there in Proverbs 3.