Exodus 25:21

Place the cover on top of the ark and put in the ark the Testimony, which I will give you.

(New International Version)

'You shall put the mercy seat on top of the ark, and in the ark you shall put the testimony which I will give to you.

(New American Standard Bible)

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.

(King James Version)