Deuteronomy 31:26

Side. But not within, (Menochius) according to the generality of interpreters, whom Calmet follows, Exodus xxv. 10. But here he adopts the contrary opinion of Jonathan and Grotius, and asserts that this writing, containing the 29th, 30th, and 31st chapters, on thin boards, was placed in the ark, beside the tables of the law, in the same manner as the Philistines placed it in a coffer of gold, 1 Kings vi. 8. We read (3 Kings viii. 9,) that there was nothing in the ark except the two tables, which might be true at the time that book was written; though St. Paul (Hebrews ix. 4,) tells us, that the golden pot, and the rod of Aaron, were in the ark. If they were there in the days when the author of the first book of Kings lived, the passage in question must be understood with these exceptions. (Calmet)

This difficulty cannot, however, be now easily decided, as the Scripture often uses the word in to denote near to, &c., ver. 14. The coffer of the Philistines might also be on the outside of the ark. (Haydock)

Thee. This act of ratification of the covenant, which had been made at Horeb, 39 years before, (Calmet) was placed in or near the ark. (Haydock)

The three chapters, of which it probably consisted, seem to have been what was discovered in the reign of Josias; as the threats and blessings which they contain, would naturally tend to make a strong impression upon all, 4 Kings xxii. 8. (Calmet)

Kennicott thinks that Helcias discovered the very manuscript, which Moses had written with his own hand, and which he deposited neither in, nor fastened to any side of the ark, but only placed by the side (mitsad, juxta, Noldius) of it, or upon the same table; so that it might not be taken by the Philistines, but kept in some suitable place. (Dis. ii.) It is surprising that Huet cites Jonathan as delivering this sentiment, in capsâ ad latus dextrum. (Haydock)