United in God’s mercy

Mark 9:38-40

This man, whose case John had taken up, and thus had given occasion for the Lord to commence the discourse referred to, was not separating himself from the society of the disciples to any such effect as to scorn it like a heretic. But his position was something parallel to the familiar one of men who, while not going the length yet of receiving the sacraments of Christ, nevertheless favour the Christian name so far as even to receive Christians, and accommodate themselves to them for this very reason, and none other, that they are Christian; of which type of persons it is that He tells us that they do not lose their reward. This does not mean, however, that they ought at once to think themselves quite safe and secure simply on account of this kindness which they cherish towards Christians, while at the same time they are neither cleansed by Christ's baptism, nor incorporated into the unity of His body. But the important thing is, that they are now being guided by the mercy of God in such a way that they may also come to these higher things, and so quit this present world in safety. And such persons assuredly are more reliable, even before they become associated with the number of Christians, than those individuals who, while already bearing the Christian name and partaking in the Christian sacraments, recommend courses which are only fitted to drag others, whom they may persuade to adopt them, along with themselves into eternal punishment.

We must observe, however, that in our good works we must sometimes avoid the offense of our neighbor, sometimes look down upon the work as of no moment. For in as far as we can do it without sin, we ought to avoid the offense of our neighbour; but if a stumbling block is laid before men in what concerns the truth, it is better to allow the offense to arise, than that the truth should be abandoned.

Reference:
Harmony of the Gospels, Book IV, Ch. 6 (St. Augustine)
Homilies on Ezekiel Book 1, Homily 7 (St. Gregory the Great)