Exodus 26:34

You shall put the mercy seat on the ark of the testimony in the holy of holies.

Exodus 25:21

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.

Exodus 40:20

Then he took the testimony and put it into the ark, and attached the poles to the ark, and put the mercy seat on top of the ark.

Hebrews 9:5

and above it were the cherubim of glory overshadowing the mercy seat; but of these things we cannot now speak in detail.

Treasury of Scripture Knowledge

Summary

And thou shalt put the mercy seat upon the ark of the testimony in the most holy place.

General references

Bible References

Put the mercy seat

Exodus 25:21
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.
Exodus 40:20
Then he took the testimony and put it into the ark, and attached the poles to the ark, and put the mercy seat on top of the ark.
Hebrews 9:5
and above it were the cherubim of glory overshadowing the mercy seat; but of these things we cannot now speak in detail.

General references

Exodus 40:3
You shall place the ark of the testimony there, and you shall screen the ark with the veil.
Mark 15:38
And the veil of the temple was torn in two from top to bottom.