24 For in this sense also we may interpret without absurdity the declaration of the blessed Apostle Paul, when he says, "Having in a readiness to revenge all disobedience, when your obedience is fulfilled." Whence also the Lord Himself bids the guests in the first instance to be invited to His great supper, and afterwards compelled; for on His servants making answer to Him, "Lord, it is done as You have commanded, and yet there is room," He said to them, "Go out into the highways and hedges, and compel them to come in." In those, therefore, who were first brought in with gentleness, the former obedience is fulfilled; but in those who were compelled, the disobedience is avenged.
For what else is the meaning of "Compel them to come in," after it had previously said, "Bring in," and the answer had been made, "Lord, it is done as You commanded, and yet there is room"? If He had wished it to be understood that they were to be compelled by the terrifying force of miracles, many divine miracles were rather wrought in the sight of those who were first called, especially in the sight of the Jews, of whom it was said, "The Jews require a sign;" and, moreover, among the Gentiles themselves the gospel was so commended by miracles in the time of the apostles, that had these been the means by which they were ordered to be compelled, we might rather have had good grounds for supposing, as I said before, that it was the earlier guests who were compelled.
Wherefore, if the power which the Church has received by divine appointment in its due season, through the religious character and the faith of kings, be the instrument by which those who are found in the highways and hedges— that is, in heresies and schisms— are compelled to come in, then let them not find fault with being compelled, but consider whether they be so compelled. The supper of the Lord is the unity of the body of Christ, not only in the sacrament of the altar, but also in the bond of peace. Of the Donatists themselves, indeed, we can say that they compel no man to any good thing; for whomsoever they compel, they compel to nothing else but evil.
Source: Letters (New Advent)