Genesis 13:14 - Ellicott's Commentary On The Whole Bible

The Lord said unto Abram. — The departure of Lot was certainly a great grief to Abram; for he lost thereby the companionship of the relative who had shared his abandonment of his country, and whom, probably, in his childless state, he had regarded as his heir. Jehovah, therefore, consoles him by a more definite promise of the possession of the whole land of which he had so generously given Lot the choice, and by the assurance that his own seed should be numerous as the dust of the earth. We may also feel sure that as Lot was deteriorating, so Abram was drawing nearer to God, and walking more closely with Him; and hence the fuller assurance of the Divine blessing.