Numbers 7:89
And when Moses was gone into the tabernacle of the congregation to speak with him, then he heard the voice of one speaking unto him from off the mercy seat that was upon the ark of testimony, from between the two cherubims: and he spake unto him.
After the tabernacle was completed, Moses entered to speak with God and heard an audible voice calling him near from the divine glory above the mercy seat. That voice spoke from between the two cherubim, where the Shekinah manifested God's presence. The mercy seat stood over the ark containing the Ten Commandments, which were the basis of God's covenant with Israel.
The ark with its mercy seat was thus the place where God's presence met with His people to communicate with them and to make His will known to Moses. The voice that called Moses near gave him further directions about worship in the sanctuary. In the most holy place the high priest also sought God's direction, and God often answered with an audible voice, while at other times a light upon the cherub at the right signified favor and a cloud at the left signified refusal.