As the LORD commanded Moses, so Aaron placed it before the testimony to be kept.
God having provided manna to be his people's food in the wilderness, and to be to them a continual feast, we are here told, 1. How the memory of it was preserved. An omer of this manna was laid up in a golden pot, as we are told (Heb 9:4), and kept before the testimony, or the ark, when it was afterwards made, Exo 16:32-34.
Commenting on Exodus 16:32-36
As the LORD commanded Moses, so Aaron laid it up before the Testimony, to be kept. (p) That is, the Ark of the covenant that is, after the Ark was made.
Laid it up before the testimony - The עדות eduth or testimony belonged properly to the tabernacle, but that was not yet built. Some are of opinion that the tabernacle, built under the direction of Moses, was only a renewal of one that had existed in the patriarchal times. See Clarke's note on Exo 16:9.