Albert Barnes Commentary Deuteronomy 27:3

"and thou shalt write upon them all the words of this law, when thou art passed over; that thou mayest go in unto the land which Jehovah thy God giveth thee, a land flowing with milk and honey, as Jehovah, the God of thy fathers, hath promised thee." — Deuteronomy 27:3 (ASV)

All the words of this law - that is, all the laws revealed from God to the people by Moses, regarded by the Jews as 613 (compare Numbers 15:38 note). The exhibition of laws in this manner on stones, pillars, or tables, was familiar to the ancients. The laws were probably engraved in the stone (very plainly,Deuteronomy 27:8 is by some rendered “scoop it out well”), as are for the most part the Egyptian hieroglyphics, the plaster being afterward added to protect the inscription from the weather.