Exodus 39:35

the ark of the Testimony, its carrying poles and the mercy seat;

Exodus 25:17

“You shall make a mercy seat (cover) of pure gold, two and a half cubits long and one and a half cubits wide.

Hebrews 9:5

and above the ark were the [golden] cherubim of glory overshadowing the mercy seat; but we cannot now go into detail about these things.

Hebrews 9:8

By this the Holy Spirit signifies that the way into the Holy Place [the true Holy of Holies and the presence of God] has not yet been disclosed as long as the first or outer tabernacle is still standing [that is, as long as the Levitical system of worship remains a recognized institution],

Treasury of Scripture Knowledge

Summary

The ark of the testimony, and the staves thereof, and the mercy seat,

The mercy seat

Bible References

The mercy seat

Exodus 25:17
“You shall make a mercy seat (cover) of pure gold, two and a half cubits long and one and a half cubits wide.
Hebrews 9:5
and above the ark were the [golden] cherubim of glory overshadowing the mercy seat; but we cannot now go into detail about these things.