Hadith: No people sit in a gathering in which they do not remember Allah and do not invoke blessings upon their Prophet, except that it will be a source of regret for them. If He wills, He will punish them, and if He wills, He will forgive them

عَنْ أَبِي هُرَيْرَةَ رضي الله عنه، عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ:
«مَا جَلَسَ قَوْمٌ مَجْلِسًا لَمْ يَذْكُرُوا اللَّهَ فِيهِ وَلَمْ يُصَلُّوا عَلَى نَبِيِّهِمْ إِلاَّ كَانَ عَلَيْهِمْ تِرَةً، فَإِنْ شَاءَ عَذَّبَهُمْ وَإِنْ شَاءَ غَفَرَ لَهُمْ».
[صحيح] - [رواه أبو داود والترمذي والنسائي في الكبرى] - [سنن الترمذي: 3380]

Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said:
"No people sit in a gathering in which they do not remember Allah and do not invoke blessings upon their Prophet, except that it will be a source of regret for them. If He wills, He will punish them, and if He wills, He will forgive them."
[Authentic hadith] - - [Sunan At-Termedhy - 3380]

Explanation

The Prophet (may Allah's peace and blessings be upon him) warned against neglecting the remembrance of Allah, stating that no group of people sit in a gathering where they do not remember Allah Almighty and do not invoke blessings upon His Messenger (may Allah's peace and blessings be upon him), except that such a gathering will be a source of regret, remorse, loss, and deficiency for them on the Day of Judgment. If Allah wills, He will punish them for their past sins and future shortcomings, and if He wills, He will forgive them out of His grace and mercy.