Luke 9:50

Therefore in heretics and false catholics, it becomes us to abhor, and forbid not the common sacraments in which they are with us, and not against us, but the divisions contrary to peace and truth, wherein they are against us as following not the Lord.

And Jesus said to him: Do not forbid him. For whoever is not against you is for you. Taught by this saying, the Apostle says: But whether in pretense or in truth Christ is proclaimed, and in this I rejoice, yes, and will rejoice (Philippians 1). But although he rejoices even in those who proclaim Christ insincerely, such people sometimes doing signs in the name of Christ are considered not to be prohibited for the sake of others' salvation, however, their own conscience is not made secure through such signs. Rather, on that day when they say: Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name? they will receive a reply: I never knew you, depart from me, you workers of lawlessness (Matthew 7). Therefore, in heretics and evil Catholics, it is not the common sacraments, which are with us and not against us, but the division contrary to peace and truth, which is not with us and they do not follow the Lord with us, that we ought to detest and prohibit.

Now John is not blamed, because he did this from love, but he is taught to know the difference between the strong and the weak. And therefore our Lord though He rewards the stronger, yet does not exclude the weak; as it follows, And Jesus said unto him, Forbid him not, for he that is not against you is for you. True, O Lord. For both Joseph and Nicodemus, through fear Thy secret disciples, when the time came, did not refuse their offices. But still since Thou saidst elsewhere, He that is not with me is against me, and he that gathereth not with me scattereth, (Luke 11:23.) explain unto us lest the two seem contrary to one another. And it seems to me, if any one considers the Searcher of hearts, he cannot doubt that every man's action is distinguished by the motive of his heart. Now why does He in this place say that they are not to be hindered, who by the imposition of hands can subdue the unclean spirits, when according to Matthew, He says to these, I never knew you? (Matt. 7:23.) But we ought to perceive that there is no difference of opinion, but that the decision is this, that not only the official works but works of virtue are required in a priest, and that the name of Christ is so great, that even to the unholy it serves to give defence, but not grace. Let no one then claim to himself the grace of cleansing a man, because in him the power of the eternal Name has worked. For not by thy merits, but by his own hatred, the devil is conquered.