10 Listen also for the thirty pieces of silver. And I will say to them, If it be good in your sight, give me my price, or refuse, and the rest. One price is owing to Me from you for My healing the blind and lame, and I receive another; for thanksgiving, dishonour, and for worship, insult. Do you see how the Scripture foresaw these things? And they weighed for My price thirty pieces of silver. How exact the prophecy! How great and unerring the wisdom of the Holy Ghost! For he said, not ten, nor twenty, but thirty, exactly as many as there were. Tell also what becomes of this price, O Prophet! Does he who received it keep it? Or does he give it back? And after he has given it back, what becomes of it? The Prophet says then, And I took the thirty pieces of silver, and cast them into the house of the Lord, into the foundry. Compare the Gospel with the Prophecy: Judas, it says, repented himself, and cast down the pieces of silver in the temple, and departed.
Source: Catechetical Lectures (New Advent)