Exodus 40:20

“And he took and put the testimony into the ark, etc.] The ten commands, called the “testimony”, because they testified and declared what was the will of God with respect to things to be done, or not done. The Targum of Jonathan says, he put the broken pieces of the tables into it; but what became of them, or were done with them, we nowhere read; and it does not appear that any other, but those that Moses hewed by the order of God, were put into the ark; (see <051001>Deuteronomy 10:1-5) and set the staves on the ark; that it might be ready to be carried whenever a remove was necessary: and put the mercy seat above upon the ark; together with the cherubim.”

“The testimony - i. e. the tables of stone with the Ten Commandments engraved on them Exodus 25:16; Exodus 31:18. Nothing else is said to have been put into the ark. These were found there by themselves in the time of Solomon 1 Kings 8:9; 2 Chronicles 5:10. The pot of manna was “laid up before the testimony” Exodus 16:34; Aaron’s rod was also placed “before the testimony” Numbers 17:10; and the book of the law was put at “the side of the ark” Deuteronomy 31:26. The expression “before the testimony” appears to mean the space immediately in front of the ark. Most interpreters hold that the pot of manna and Aaron’s rod were at first placed between the ark and the veil, and afterward within the…”

“the testimony: Exo 16:34, Exo 25:16-21, Exo 31:18; Psa 40:8; Mat 3:15 mercy: Exo 40:3, Exo 37:6-9; Rom 3:25, Rom 10:4; Heb 4:16, Heb 10:19-21; Jo1 2:2 Exodus 40:21”

“Arrangement of the ark. "He took and put the testimony into the ark." העדוּת does not mean "the revelation, so far as it existed already, viz., with regard to the erection of the sanctuary and institution of the priesthood (ch. 25-31), and so forth," as Knobel arbitrarily supposes, but "the testimony," i.e., the decalogue written upon the two tables of stone, or the tables of the covenant with the ten words; "the testimony," therefore, is an abbreviated expression for "the tables of testimony" ( Exo 31:18, see at Exo 25:16). After the ark had been brought into the dwelling, he "hung the curtain" (vail, see at Exo 26:31; lit., placed it upon the hooks of the pillars), "and so covered over the…”