Joseph Benson's Commentary of the Old and New Testaments - Exodus 20:24
Exodus 20:24. An altar of earth It is meant of occasional altars, such as they reared in the wilderness before the tabernacle was erected, and afterward upon special emergencies, for present use. They are appointed to make these very plain, either of earth or of unhewn stones. That they might not be tempted to think of a graven image, they must not so much as hew the stones into shape that they made their altars of, but pile them up as they were in the rough. In all places... read more
Albert Barnes' Notes on the Whole Bible - Exodus 20:22-26
Nothing could be more appropriate as the commencement of the book of the covenant than these regulations for public worship. The rules for the building of altars must have been old and accepted, and are not inconsistent with the directions for the construction of the altar of the court of the tabernacle, Exodus 27:1-8 (compare Joshua 22:26-28). read more