John Calvin Commentary Jude 1:22

"And on some have mercy, who are in doubt;" — Jude 1:22 (ASV)

And of some have compassion. He adds another exhortation, showing how the faithful ought to act in reproving their brothers, in order to restore them to the Lord. He reminds them that they should be treated in different ways, each according to their disposition: for to the meek and teachable we should show kindness; but others, who are hard and perverse, must be subdued by terror. This is the difference which he mentions.

The participle διακρινόμενοι, I do not know why this is rendered in a passive sense by Erasmus. It may indeed be rendered in either way, but its active meaning is more suitable to the context. The meaning then is, that if we wish to care for the well-being of those who go astray, we must consider the character and disposition of each one. Consequently, those who are meek and tractable may be kindly restored to the right way, as they are objects of pity; however, if any are perverse, such a person is to be corrected with more severity. And since harshness is almost hateful, he excuses it on the grounds of necessity, because otherwise, those who do not willingly follow good advice cannot be saved.

Moreover, he employs a striking metaphor. When there is a danger of fire, we do not hesitate to violently snatch away those whom we desire to save, for it would not be enough to beckon with the finger or kindly extend the hand. In the same way, the salvation of some must be cared for, because they will not come to God unless they are forcefully drawn.

The old translation is very different, a reading that is, however, found in many of the Greek copies; the Vulgate says, “Rebuke the judged” (Arguite dijudicatos). But the first meaning is more suitable and is, I believe, according to the old and genuine reading. The phrase to save is applied to humans, not because they are the authors of salvation, but its ministers.