Riyad as-Salihin

Abu Hurairah (May Allah be pleased with him) reported: The Prophet (ﷺ) said, "Whenever a group of people sit in a gathering in which they do not remember Allah the Exalted, nor supplicate to elevate the rank of their Prophet, such a gathering will be a cause of grief to them. If Allah wills, He will punish them, and if He wills He will forgive them."

[At-Tirmidhi].