Exodus 25:17

Mercy-seat, or, propitiatory; which seems from the sameness of dimensions to be nothing else but the covering of the ark, upon which God is said to sit, whence the ark is called God's footstool. This covering is a manifest type of Christ, who is therefore called the propitiation, or propitiatory, Romans 3:25 1 John 2:2, 1 John 4:10, because he interposeth himself between God our Judge, and the law, by which we all stand condemned and accursed, Galatians 3:10,13; that God may not deal rigorously with us according to that law, but mercifully for his sake who hath fulfilled the law, and therefore boldly presents himself to his Father on our behalf.