John Wesley on Joshua 24:26

These words - That is, this covenant or agreement of the people with the Lord. In the book - That is, in the volume which was kept in the ark, Deut 31:9,26, whence it was taken and put into this book of Joshua: this he did for the perpetual remembrance of this great and solemn action, to lay the greater obligation upon the people to be true to their engagement; and as a witness for God, against the people, if afterward he punished them for their defection from God, to whom they had so solemnly and freely obliged themselves. Set it up - As a witness and monument of this great transaction, according to the custom of those ancient times. Possibly this agreement was written upon this stone, as was then usual. By the sanctuary - That is, near the place where the ark and tabernacle then were; for tho' they were forbidden to plant a grove of trees near unto the altar, as the Gentiles did, yet they might for a time set up an altar, or the ark, near a great tree which had been planted there before.