Christ the Head and the abiding gift of the Spirit.
Archimandrite Nikifor’s Biblical Encyclopedia
To believe in the Church is reverently to honor Christ’s true Church and to receive her teaching and commandments, trusting that saving grace abides, acts, teaches, and governs within her. Her one eternal Head is the God-man Jesus Christ, full of grace and truth, who fills His body, the Church. He promised the disciples another Comforter to remain with them forever (John 14:16), and the Holy Spirit appoints shepherds to care for the Church of God, purchased with Christ’s blood (Acts 20:28).
Therefore Christ’s promise stands: “I will build My Church, and the gates of Hades shall not prevail against it,” and “I am with you always, to the end of the age” (Matt. 16:18; 28:20).