Starting at verse 20, chapter 5, in the book of 2 Kings, Elisha's servant Gehazi discovered that the Syrian army commander, whom Elisha had healed from leprosy, had went away without Elisha taking his gifts.
The servant lied to Naaman, telling him that two prophets had arrived and would like some of the gifts he offered Elisha. Naaman did without question, for he was pleased to part with the gifts in exchange for healing his leprosy.
The servant hid the gifts and lied to Elisha about where he had gone.
But Elisha knew what he had done, and because of it Naaman's leprosy was upon him and his children. Forever.