Now when the prince shall prepare a voluntary burnt offering or peace offerings voluntarily unto the LORD, one shall then open him the gate that looketh toward the east, and he shall prepare his burnt offering and his peace offerings, as he did on the sabbath day: then he shall go forth; and after his going forth one shall shut the gate.
When the prince wants to give a special gift to God, the person in charge opens the east gate. He prepares the offering like on a rest day. Then, he leaves, and someone closes the gate behind him.