Love of God and neighbor binds the church
Augustine has just finished the faith about God as creator and renewer, and now turns to the article of the creed on the holy catholic church, grounding it in the twofold command of love.
But since love has been commanded not only toward God, when it was said, “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind” (Deuteronomy 6:5), but also toward the neighbor—for he says, “You shall love your neighbor as yourself” (Leviticus 19:18)—unless this faith holds to the gathering and fellowship of human beings, in which brotherly love is at work, it is less fruitful. Therefore we believe also in the holy church, certainly the catholic church.
For heretics and schismatics call their own gatherings churches. But heretics violate the faith itself by thinking falsely about God; schismatics, however, leap apart from brotherly love by wicked divisions, even though they believe the same things we believe. For this reason neither heretics belong to the catholic church, because she loves God, nor do schismatics, because she loves the neighbor. And so she readily forgives the sins of her neighbor, because she prays to be forgiven by him who reconciled us to himself, blotting out all past things and calling us to a new life. Until we lay hold of that life in its perfection, we cannot be without sins; but it matters what kind they are.
Latin
Sed quoniam dilectio non tantum in deum nobis imperata est, cum dictum est: diliges dominum deum tuum ex toto corde tuo, et ex tota anima tua, et ex tota mente tua, sed etiam in proximum — nam, diliges, inquit, proximum tuum tamquam te ipsum - nisi autem ista fides congregationem societatemque hominum teneat, in qua fraterna caritas operetur, minus fructuosa est, credimus et in sanctam ecclesiam, utique catholicam.
nam haeretici et schismatici congregationes suas ecclesias uocant. sed haeretici de deo falsa sentiendo ipsam fidem uiolant; schismatici autem discissionibus iniquis a fraterna caritate dissiliunt, quamuis ea credant quae credimus. quapropter nec haeretici pertinent ad ecclesiam catholicam, quoniam diligit deum, nec schismatici, quoniam diligit proximum. et ideo peccatis proximi facile ignoscit, quia sibi precatur ignosci ab illo, qui nos reconciliauit sibi, delens omnia praeterita et ad uitam nouam nos uocans: quam uitam donec perfectam capiamus, sine peccatis esse non possumus; interest tamen qualia sint.