3 Believe thou In One Lord Jesus Christ, the Only-Begotten Son of God. For we say “One Lord Jesus Christ,” that His Sonship may be “Only-begotten:” we say “One,” that you may not suppose another: we say “One,” that you may not profanely diffuse the many names of His action among many sons. For He is called a Door; but take not the name literally for a thing of wood, but a spiritual, a living Door, discriminating those who enter in. He is called a Way, not one trodden by feet, but leading to the Father in heaven; He is called a Sheep, not an irrational one, but the one which through its precious blood cleanses the world from its sins, which is led before the shearers, and knows when to be silent.
This Sheep again is called a Shepherd, who says, I am the Good Shepherd: a Sheep because of His manhood, a Shepherd because of the loving-kindness of His Godhead. And would you know that there are rational sheep? The Saviour says to the Apostles, Behold, I send you as sheep in the midst of wolves. Again, He is called a Lion, not as a devourer of men, but indicating as it were by the title His kingly, and steadfast, and confident nature: a Lion He is also called in opposition to the lion our adversary, who roars and devours those who have been deceived. For the Saviour came, not as having changed the gentleness of His own nature, but as the strong Lion of the tribe of Judah, saving them that believe, but treading down the adversary.
He is called a Stone, not a lifeless stone, cut out by men's hands, but a chief corner-stone, on whom whosoever believes shall not be put to shame.
Source: Catechetical Lectures (New Advent)