Exodus 25:17 is the original command to make the mercy seat, which is listed here as completed.

Hebrews 9:5 describes the cherubim of glory overshadowing the mercy seat, giving NT context to this item.

Hebrews 9:4 mentions the ark of the covenant with the mercy seat above it, directly referencing this item.

Hebrews 9:8 explains the symbolic meaning of the Holy of Holies, where the mercy seat resides, about restricted access.