John Wesley on Jude 1:19

These are they who separate themselves, sensual, not having the Spirit - Having natural senses and understanding only, not the Spirit of God; otherwise they could not separate. For that it is a sin, and a very heinous one, "to separate from the church," is out of all question. But then it should be observed, That by the church is meant a body of living Christians, who are "an habitation of God through the Spirit:" That by separating is understood, renouncing all religious intercourse with them; no longer joining with them in solemn prayer, or the other public offices of religion: and, That we have no more authority from scripture to call even this schism, than to call it murder.