17 Peter was not with Ananias and Sapphira when they sold their possessions, but he was present by the Spirit; Why, he says, has Satan filled your heart to lie to the Holy Ghost? There was no accuser; there was no witness; whence knew he what had happened? Whiles it remained was it not your own? And after it was sold, was it not in your own power? Why have you conceived this thing in your heart? The unlettered Peter, through the grace of the Spirit, learned what not even the wise men of the Greeks had known.
You have the like in the case also of Elisseus. For when he had freely healed the leprosy of Naaman, Gehazi received the reward, the reward of another's achievement; and he took the money from Naaman, and bestowed it in a dark place. But the darkness is not hidden from the Saints. And when he came, Elisseus asked him; and like Peter, when he said, Tell me whether you sold the land for so much? He also enquires, Whence do you come, Gehazi? Not in ignorance, but in sorrow ask I whence do you come?
From darkness are you come, and to darkness shall you go; you have sold the cure of the leper, and the leprosy is your heritage. I, he says, have fulfilled the bidding of Him who said to me, Freely you have received, freely give; but you have sold this grace; receive now the condition of the sale. But what says Elisseus to him? Went not mine heart with you? I was here shut in by the body, but the spirit which has been given me of God saw even the things afar off, and showed me plainly what was doing elsewhere. Do you see how the Holy Ghost not only rids of ignorance, but invests with knowledge? Do you see how He enlightens men's souls?
Source: Catechetical Lectures (New Advent)