The altar was a place to meet with God, to offer sacrifice for sin, to show submission to God, and to worship God.
Abram never lived in a house – he lived in a tent. Tents are the home of those who are just passing through and do not put down permanent roots.
But God is in the business of growing Abram into a man of great faith, and this requires circumstances where Abram must trust God. “Faith is not a mushroom that grows overnight in damp soil; it is an oak tree that grows for a thousand years under the blast of the wind and rain.” (Barnhouse).
