Why did God give the mercy seat?
The mercy seat was provided because God's law is so demanding that no one can satisfy it. The cherubim covering the ark indicated God's mercy, and mercy alone could answer to the law inside. Scripture teaches all have sinned, yet are justified freely by His grace through redemption in Christ Jesus.
Les explains that the cherubim were two angelic-like beings whose wings met over the middle of the little box made of pure beaten gold. Those cherubim indicated a covering of God's mercy. God's mercy is the only thing that could answer to what was in the box—the law. The law is so demanding that there is only one way we can even come close to satisfying its demand, and that is in God's mercy. That is why the mercy seat existed. Les then ties this to Romans 3:23–25, where Paul, by the Holy Spirit, concludes that all have sinned and come short of the glory of God, every human being back to Adam, Jew and Gentile. Yet believers are justified freely by His grace through the redemption that is in Christ Jesus, whom God hath set forth. Les also notes that the more interested a person is in real Bible study, the more glorious this tabernacle becomes.