And Aaron placed it in front of the Testimony, to be preserved just as the LORD had commanded Moses.
An omer of manna laid up in a golden pot before the ark was a standing miracle, meant to silence every murmur. Posterity would see what sort of food sustained them, and judge whether they had cause to complain or reason to thank God; eaten bread must not be forgotten. The manna never failed them forty years, though Israel was provoking, thus God's providence is constant, and Christ Himself is the true manna, the bread of life.
AI summary
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.