Or, after thou shalt have put in the ark; for the ark was not to be opened after the covering was put upon it. The Hebrew particle vau oft signifies after that, as Jeremiah 43:13, Jeremiah 51:60.
Related Commentaries of Exodus 25:21
Exodus 25:21
21 And thou shalt put the mercy seat above upon the ark; and in the ark thou shalt put the testimony that I shall give thee.