Imam Al-Nawawi’s Riyad-us-Saliheen
Chapter 274
Prohibition of Rejoicing over another’s Trouble

Allah, the Exalted, says:

“The believers are nothing else than brothers (in Islamic religion).” (49:10)

“Verily, those who like that (the crime of) illegal sexual intercourse should be propagated among those who believe, they will have a painful torment in this world and in the Hereafter.” (24:19)

1577. Wathilah bin Al-Asqa` (May Allah be pleased with him) said: The Messenger of Allah (sallallaahu ’alayhi wa sallam) said, “Do not express pleasure at the misfortune of a (Muslim) brother lest Allah should bestow mercy upon him and make you suffer from a misfortune.”
[At-Tirmidhi].