From his Commentary on the Apostles’ Creed (36-38):
Whence also the Apostle says, “All Scripture given by inspiration of God is profitable for instruction.” And therefore it seems proper in this place to enumerate, as we have learned from the tradition of the Fathers, the books of the New and of the Old Testament, which, according to the tradition of our forefathers, are believed to have been inspired by the Holy Ghost, and have been handed down to the Churches of Christ.
Of the Old Testament, therefore, first of all there have been handed down five books of Moses, Genesis, Exodus, Leviticus, Numbers, Deuteronomy; Then Jesus Nave, (Joshua the son of Nun), The Book of Judges together with Ruth; then four books of Kings (Reigns), which the Hebrews reckon two; the Book of Omissions, which is entitled the Book of Days (Chronicles), and two books of Ezra (Ezra and Nehemiah), which the Hebrews reckon one, and Esther; of the Prophets, Isaiah, Jeremiah, Ezekiel, and Daniel; moreover of the twelve (minor) Prophets, one book; Job also and the Psalms of David, each one book. Solomon gave three books to the Churches, Proverbs, Ecclesiastes, Canticles. These comprise the books of the Old Testament.
Of the New there are four Gospels, Matthew, Mark, Luke, John; the Acts of the Apostles, written by Luke; fourteen Epistles of the Apostle Paul, two of the Apostle Peter, one of James, brother of the Lord and Apostle, one of Jude, three of John, the Revelation of John. These are the books which the Fathers have comprised within the Canon, and from which they would have us deduce the proofs of our faith.
But it should be known that there are also other books which our fathers call not “Canonical” but “Ecclesiastical:” that is to say, Wisdom, called the Wisdom of Solomon, and another Wisdom, called the Wisdom of the Son of Sirach, which last-mentioned the Latins called by the general title Ecclesiasticus, designating not the author of the book, but the character of the writing. To the same class belong the Book of Tobit, and the Book of Judith, and the Books of the Maccabees. In the New Testament the little book which is called the Book of the Pastor of Hermas, [and that] which is called The Two Ways, or the Judgement of Peter; all of which they would have read in the Churches, but not appealed to for the confirmation of doctrine. The other writings they have named “Apocrypha.” These they would not have read in the Churches.
These are the traditions which the Fathers have handed down to us, which, as I said, I have thought it opportune to set forth in this place, for the instruction of those who are being taught the first elements of the Church and of the Faith, that they may know from what fountains of the Word of God their draughts must be taken.
Those of you who are counting will recognise Rufinus’ list of the canon of Scripture is identical to what Protestant and Evangelical churches use today (as, for the Old Testament, is the case in Judaism as well.)
Rufinus’ distinction between “canonical” and “ecclesiastical” is replicated in Article VI of the Anglican Articles of Religion, although there it’s attributed to Jerome. Jerome’s opinion on the subject is discussed in my Apologetics for the Rest of Us.