Here ya go.
“But who can fail to be aware that the sacred canon of Scripture, both of the Old and New Testament, is confined within its own limits, and that it stands so absolutely in a superior position to all later letters of the bishops, that about it we can hold no manner of doubt or disputation whether what is confessedly contained in it is right and true; but that all the letters of bishops which have been written, or are being written, since the closing of the canon, are liable to be refuted if there be anything contained in them which strays from the truth, either by the discourse of some one who happens to be wiser in the matter than themselves, or by the weightier authority and more learned experience of other bishops, by the authority of Councils; and further, that the Councils themselves, which are held in the several districts and provinces, must yield, beyond all possibility of doubt, to the authority of plenary Councils which are formed for the whole Christian world; and that even of the plenary Councils, the earlier are often corrected by those which follow them, when, by some actual experiment, things are brought to light which were before concealed, and that is known which previously lay hid, and this without any whirlwind of sacrilegious pride, without any puffing of the neck through arrogance, without any strife of envious hatred, simply with holy humility, catholic peace, and Christian charity” (Augustine “On Baptism, Against the Donatists”, II.III.IV).
Around 413 he stated in a letter to Fortunatianus: I have thought it my duty to quote all these passages from the writings of both Latin and Greek authors who, being in the Catholic Church before our time, have written commentaries on the divine oracles, in order that our brother, if he hold any different opinion from theirs, may know that it becomes him, laying aside all bitterness of controversy, and preserving or reviving fully the gentleness of brotherly love, to investigate with diligent and calm consideration either what he must learn from others, or what others must learn from him. For the reasonings of any men whatsoever, even though they be Catholics, and of high reputation, are not to be treated by us in the same way as the canonical Scriptures are treated. We are at liberty, without doing any violence to the respect which these men deserve, to condemn and reject anything in their writings, if perchance we shall find that they have entertained opinions differing from that which others or we ourselves have, by the divine help, discovered to be the truth. I deal thus with the writings of others, and I wish my intelligent readers to deal thus with mine. (*NPNF1: Vol. I, Letters of St. Augustine, Letter 148, §15. *)
That is how he was defined in reference to his book on covenant theology.
