13 My Brethren, does ever either Presbyter or Bishop come up here, and say anything from this higher place, but that the property of others must not be plundered, that there must be no fraud committed, no wickedness done? They cannot say ought else who sit in Moses' seat, and it is it that speaks by them, not they themselves. What then is, “Do men gather grapes of thorns, or figs of thistles?” and, “Every tree is known by his fruit”? Can a Pharisee speak good things?
A Pharisee is a thorn; how from a thorn do I gather grapes? Because You, Lord, have said, “What they say, do; but what they do, do not.” Do You bid me gather grapes of thorns when You say, “Do men gather grapes of thorns”? The Lord answers you, “I have not bidden you gather grapes of thorns: but look, mark well, if haply, as is often the case, the vine when it trails all along upon the ground, be not entangled in thorns.” For we sometimes find this, my Brethren, a vine planted over sedge, how it has there a thorny hedge, and throws out its branches, and entangles them in the thorny hedge, and the grape hangs among the thorns; and he that sees it plucks the grape, yet not from the thorns, but from the vine which is entangled in the thorns.
In like manner then the Pharisees are thorny; but by sitting in Moses' seat, the vine wraps them round, and grapes, that is, good words, good precepts, hang from them. If you pick the grape, the thorn will not prick you, when you read, “What they say, do; but what they do, do not.” But the thorn will prick you, if you do what they do. So then that you may gather the grape, and not be caught in the thorns, “What they say, do; but what they do, do not.” Their deeds are the thorns, their words are the grapes, but from the vine, that is, from Moses' seat.
Source: Sermons on Selected Lessons of the New Testament (New Advent)