Charles Spurgeon Commentary Genesis 22:9

"And they came to the place which God had told him of. And Abraham built the altar there, and laid the wood in order, and bound Isaac his son, and laid him on the altar, upon the wood." — Genesis 22:9 (ASV)

And they came to the place which God had told him of; and Abraham built an altar there,

See him pulling out the large, rough, unhewn stones that lay round about the place, and then fling them up into an altar.