St. Augustine.
"This is the holy Church, the one Church, the true Church, the Catholic Church fighting against all heresies. Fight it can; be fought down, it cannot. Let us love Our Lord God, let us love His Church, Him as a father, Her as a mother; Him as Lord, Her as His handmaid. No man offends the one and wins the favor of the other. He will not have God for his father who refuses the Church for his mother. “What does it profit you not to have offended your father, since he will punish your offenses against your mother? What does it profit you to praise the Lord, to honor Him, to preach Him, to believe in His Son, to confess that He sits at the right hand of God the Father, while at the same time you denigrate His Church? Outside the Church you can find everything except salvation. You can have dignities. You can have sacraments. You can sing ‘Alleluia’, answer ‘Amen’, have the gospels and have faith in the name of the Father and of the Son and the Spirit and preach it too. But you will find salvation and all the means of grace alone in the Catholic Church.”