There was a famine in the land, or, in that land of Canaan, a land eminently fruitful, Deuteronomy 8:7,8. This was partly to punish that people's sins, Psalms 107:34, partly to try Abram's faith.
Related Commentaries of Genesis 12:10
Genesis 12:10
10 And there was a famine in the land: and Abram went down into Egypt to sojourn there; for the famine was grievous in the land.