Albert Barnes Commentary Joshua 24:26

"And Joshua wrote these words in the book of the law of God; and he took a great stone, and set it up there under the oak that was by the sanctuary of Jehovah." — Joshua 24:26 (ASV)

Consult the marginal references.

That was by the sanctuary of the Lord - that is, the spot where Abraham and Jacob had sacrificed and worshipped, and which might well be regarded by their posterity as a holy place or sanctuary. Perhaps the very altar of Abraham and Jacob was still remaining.