Surah 63:3
"That is because they believed, (and) then they disbelieved. So a seal was set on their hearts, and they do not understand."
– That is because they believed, (and) then they disbelieved
Hypocrisy is hard to spot because everything appears and sounds normal (vv. 1–4). Meanwhile, the hypocrites lead others astray (v. 2). At the heart of their problem is a loss of faith in the messenger.
- from The Quran with Christian Commentary: A Guide to Understanding the Scripture of Islam