Song of Solomon 8:9

If she is a wall, let us build on it, etc. It is customary for the Lord Himself often to be designated in Sacred Scripture by the name of a wall or door. For He is rightly called a wall because He fortifies His Church on all sides, lest it be plundered by enemies; a door rightly, because it is only through Him that we enter either the fellowship of the Church or the ramparts of the eternal kingdom. For He says of Himself, I am the door of the sheep; if anyone enters by me, he will be saved (John 10). And again, No one comes to the Father except through me (John 14). The prophet, foretelling future gifts to the Church, says of Him: A wall and a rampart will be set within it (Isaiah 26). The wall indeed is He Himself appearing in the flesh; the rampart, however, is the revelation of prophecy, which by predicting Him to be incarnate from the world's beginning, greatly aided the structure of the Church. But He who, by appearing in the flesh, deigned to make the Church His sister, also granted her the participation of His name, so that she might also be called a wall and door: a wall indeed in those who, endowed with greater knowledge and power of the Spirit, are strong enough to fortify and defend the minds of the faithful from the incursions of error by resisting the weapons of iniquity; a door in those who, though less trained to repel the sophisms of heretics or pagans, are nevertheless wholesomely imbued with the simplicity of the Catholic faith, would open the entrance of the kingdom to those who wished by preaching, and lead them through the mystery of second regeneration into the courts of the heavenly life: just as He did not refrain from bestowing other names of virtues that undoubtedly specially pertain to Him to the more perfect members of His Bride. For instance, You are the light of the world (Matthew 10), and again, Behold, I send you out as sheep among wolves (Luke 10); although He Himself is the true light that enlightens everyone coming into this world (John 1). He is the immaculate and uncontaminated Lamb who took away the sin of the world. Therefore, if she is a wall, He says, our sister, let us build upon her silver bulwarks; as if He were openly saying, If the Church of the Gentiles is suitable in some of its members, having men apt to teach, either naturally clever or instructed by philosophical training, we should not by any means deprive…