21 But I have the sacrament, you will say. You say the truth; the sacrament is divine; you have baptism, and that I confess. But what says the apostle? “If I should know all mysteries, and have prophecy and all faith, so that I could remove mountains;” in case you should say this, “I believe; enough for me.” But what says James? “The devils believe and tremble.” Faith is mighty, but without charity it profits nothing. The devils confessed Christ. Accordingly it was from believing, but not from loving, they said, “What have we to do with You?” They had faith, but not charity; hence they were devils. Boast not of faith; so far you are on a level with the devils. Say not to Christ, What have I to do with You? For Christ's unity speaks to you. Come, learn peace, return to the bowels of the dove. You have been baptized without; have fruit, and you return to the ark.
Source: Tractates on the Gospel of John (New Advent)