Mercy-seat
    (Heb. kapporeth, a "covering;" LXX. and N.T., hilasterion;
    Vulg., propitiatorium), the covering or lid of the ark of the
    covenant (q.v.). It was of acacia wood, overlaid with gold, or
    perhaps rather a plate of solid gold, 2 1/2 cubits long and 1
    1/2 broad (Ex. 25:17; 30:6; 31:7). It is compared to the throne
    of grace (Heb. 9:5; Eph. 2:6). The holy of holies is called the
    "place of the mercy-seat" (1 Chr. 28:11: Lev. 16:2).

      It has been conjectured that the censer (thumiaterion, meaning
    "anything having regard to or employed in the burning of
    incense") mentioned in Heb. 9:4 was the "mercy-seat," at which
    the incense was burned by the high priest on the great day of
    atonement, and upon or toward which the blood of the goat was
    sprinkled (Lev. 16:11-16; comp. Num. 7:89 and Ex. 25:22).