“The mercy seat”
And you are to construct a mercy seat of pure gold… Make two cherubim of hammered gold at the ends of the mercy seat. (Exodus 25:17–18 BSB)
What it sounds like today
A decorative golden lid for the ark, topped with angel figures.
The cultural key
The 'mercy seat' (kapporet) is the solid-gold cover of the ark, flanked by two cherubim whose wings arch over it, and God's presence was understood to appear in the space between them. Its name comes from the root 'to cover' or 'atone,' because once a year, on the Day of Atonement, the high priest sprinkled sacrificial blood on it for the sins of the nation. The Greek Old Testament calls it the hilasterion, and Paul uses that exact word to say God presented Christ as the place where atonement is made.
Recovered meaning
The most sacred object in Israel was a lid where blood met the presence of God and mercy 'covered' sin. Paul takes its Greek name and applies it to Jesus: the true place of atonement is now a person.