Adam Clarke on Exodus 16:34

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. The word signifies reference to something beyond itself; thus the tabernacle, the manna, the tables of stone, Aaron's rod, etc., all bore reference and testimony to that spiritual good which was yet to come, viz., Jesus Christ and his salvation.