At that time: Jesus said to his disciples: Beware of false prophets which come to you in sheep's clothing, but inwardly they are ravening wolves.
St. Hilary the Bishop
The Lord warneth us that we must rate the worth of flattering words and seeming meekness, by the fruits which they that manifest such things bring forth in their works; in other words, that we should look, in order to see what a man is, not at his professions, but at his deeds. For there are many whose sheep's clothing is but a disguise of wolfish ravening. And so the Lord asketh: Do men gather grapes of thorns, or figs of thistles? Even so every good tree bringeth forth good fruit, but a corrupt tree bringeth forth evil fruit. In which words the Lord teacheth us that men are a like case; evil men bring not forth good fruits, and hereby are we to know them. Lip-service alone winneth not the kingdom of heaven, nor is everyone that saith unto Christ, Lord, Lord, an heir thereof.
What use is there in thus calling the Lord by his title Lord? Would he not be Lord of all the same, whether or not we called him so? What holiness is there in this ascription of a name, when the true way to enter into the kingdom of heaven is to do the will of our Father, who is in heaven? Saith the Lord Christ: Many will say to me in that day: Lord, Lord, have we not prophesied in thy Name? Already here doth the Lord rebuke the deceit of the false prophets, and the feigning of the hypocrites, who take glory to themselves because of the power of their words, or their prophesying in teaching, or their casting out of devils, or such-like mighty works.
Because of all these things they promise unto themselves the kingdom of heaven, as though in their words and works any good thing were their own and not rather the mighty working of that God upon whom they call; for it is reading that bringeth knowledge of doctrine, and the Name of Christ that driveth out devils. That which is needed on our part to win that blessed eternity, that of our own which we must give, is to will to do right, to turn away from all evil. to obey with our whole heart the commandments laid on us from heaven, and so to become the friends of God. It should be ours, rather to do God's will, than to boast of God's power. And we must put off from us, and thrust away, such as are by their wicked works already estranged from his friendship.