Nicene and Post-Nicene Fathers, Ser. II, Vol. III:
Life and Works of Rufinus with Jerome's Apology Against Rufinus.: But I follow Christ in condemning all falsehood.

3. He has endeavoured, indeed, to brand us with the stain of this false teaching by speaking to some of our brethren, and he repeats this by various letters, according to his recognized plan of action. It is nothing to me what he may write or assert, but, since he raises this question about a doctrine of perjury, I will state my opinion upon it, and then leave him to pass judgment upon himself. It is this. Since our Lord and Saviour says in the Gospels “It was said to them of old time, Thou shalt not forswear thyself, but shalt pay to the Lord thy vows, but I say unto you, Swear not at all;” 2933 I say that every one who teaches that for any cause whatever we may swear falsely, is alien from the faith of Christ and from the unity of the catholic church.

Footnotes

Matt. 5:33, 34