John Gill Commentary 1 Kings 8:9

"There was nothing in the ark save the two tables of stone which Moses put there at Horeb, when Jehovah made a covenant with the children of Israel, when they came out of the land of Egypt." — 1 Kings 8:9 (ASV)

There was nothing in the ark, save the two tables of stone
which Moses put there at Horeb
That is, there were no other writings; or, as Ben Gersom says, no other part of the law, but the decalogue otherwise he observes there were in it Aaron's rod and the pot of manna, according to (Hebrews 9:4) though the particle there may be rendered "at", or "with", or "by", (See Gill on Hebrews 9:4) and so they might be not within it, but in some place on the sides of it, see (Deuteronomy 31:26) ,

when the Lord made a covenant with the children of Israel, when they
came out of the land of Egypt ;
about two months after.