Exodus 25:21

25:21 You are to put the atonement lid on top of the ark, and in the ark you are to put the testimony I am giving you.

Exodus 40:20

40:20 He took the testimony and put it in the ark, attached the poles to the ark, and then put the atonement lid on the ark.

Hebrews 9:5

9:5 And above the ark were the cherubim of glory overshadowing the mercy seat. Now is not the time to speak of these things in detail.