The mercy seat was a gold cover placed on top of the ark of the covenant. It had two gold cherubim attached at both ends. Many English Bible versions call this item the "mercy seat" (compare Exodus 25:17–22). The Hebrew word translated "mercy seat" means something like "place of atonement." It refers to the removal of God’s wrath through the offering of a gift or sacrifice.
The importance of this term comes from a ceremony on the Day of Atonement. Blood was sprinkled on the mercy seat to atone for Israel's sins (Leviticus 16). Because of this, the Most Holy Place, where the ark was kept in the temple, is called the “room for the mercy seat” in 1 Chronicles 28:11. The term "mercy seat" became common in English because of Martin Luther's German translation of the Bible. Modern translations sometimes use different terms like "atonement cover" (New International Version) or "Ark's cover" (New Living Translation).
The mercy seat was 114.3 centimeters (45 inches) long and 68.6 centimeters (27 inches) wide. The cherubim were made of gold. They faced each other with their wings spread over the ark. The space above the ark between the cherubim was where God's presence with his people was especially focused. From this place, God spoke his commands to Moses (Exodus 25:22; compare also Leviticus 16:2). Because of this connection, God is described as being "enthroned between the cherubim" (1 Samuel 4:4; 2 Samuel 6:2).
The ark itself contained the stone tablets with the Ten Commandments. These commandments summarized the covenant obligations (requirements) that the Israelites had to follow for their divine King. When the Israelites sinned against God and broke his commands, the blood sprinkled on the mercy seat made atonement for their sin and restored their relationship with God.
In the New Testament, Paul writes that Jesus is the "atoning sacrifice" through faith in his blood for all who have sinned (Romans 3:25). Here in Romans 3:25 the Greek term translated “atoning” is the same Greek word used in the Greek translation of the Old Testament (Septuagint). It is also used in Hebrews 9:5 to translate the Hebrew word for mercy seat in the Old Testament.