John Gill Commentary Genesis 12:7

"And Jehovah appeared unto Abram, and said, Unto thy seed will I give this land: and there builded he an altar unto Jehovah, who appeared unto him." — Genesis 12:7 (ASV)

And the Lord appeared to Abram
Perhaps in a human form, and so it was the Son of God; for whenever there was any visible appearance of a divine Person, under the former dispensation, it seems to be always of the essential Word, that was to be incarnate, and who spoke with an articulate voice:

and said, to your seed will I give this land ;
the whole of it inhabited by Canaanites and others; and it was for this end chiefly that Abram was called out of Chaldea into Canaan, to be shown the land, and have the grant of it for his posterity:

and there built an altar to the Lord, who appeared to him :
by way of gratitude and thankfulness for his kind and gracious appearance, and for the gift of the land of Canaan to his offspring; for on this altar he no doubt offered sacrifice in a way of thanksgiving, as Noah did when he came out of the ark.