The Prophet ﷺ said, "No people sit in a gathering in which they do not remember Allah and do not send 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."
عن النبي ﷺ قال: ما جلس قوم مجلسا لم يذكروا الله فيه، ولم يصلوا على نبيهم إلا كان عليهم ترة، فإن شاء عذبهم وإن شاء غفر لهم.
Tirmidhi (3380) and Ahmad (10277) both narrated it through Sufyan, Ahmad (9843) through Ibn Abu Dhib, Ahmad (10422) through Ziyad bin Saad, and Ibn Sunni in Amal al-Yawm wal-Layla (450) and Hakim (1/496) both through Umara bin Ghaziya, all four of them from Salih, the freedman of Tawama, from Abu Hurairah, who narrated it. Tirmidhi said, "This is a hasan hadith, and it has been narrated through more than one route from Abu Hurairah, from the Prophet ﷺ." Hakim said, "Its isnad is sahih, though the two of them did not include it, and Salih is not to be dismissed."I say, Salih the freedman of Tawama's narrations are hasan when narrated by someone who heard from him before he became confused in old age. Ibn Abu Dhib, Ziyad bin Saad, and Umara bin Ghaziya heard from him before this confusion set in. As for Sufyan Thawri, his hearing from him came after it.Similar in meaning is what Ahmad (9583) narrated, and Nasai in Amal al-Yawm wal-Layla (405, 406), both through Ibn Abu Dhib, from Saeed Maqburi, from Ishaq, or Abu Ishaq, the freedman of Abdullah bin Harith, from Abu Hurairah, who said, the Messenger of Allah ﷺ said, "No people sit in a gathering without mentioning Allah but that it is a loss upon them, and no man walks along a path without mentioning Allah but that it is a loss upon him, and no man retires to his bed without mentioning Allah but that it is a loss upon him."Ishaq the freedman of Abdullah bin Harith, or Abu Ishaq, as there is disagreement about this, Ibn Hajar said in Tahdhib, "I know nothing of his standing."Abu Dawud (4856) and Nasai in Amal al-Yawm wal-Layla (404) both narrated it through Layth, from Ibn Ajlan, from Saeed Maqburi, from Abu Hurairah, thereby dropping the intermediary between Maqburi and Abu Hurairah. Ibn Ajlan is truthful, but there has been criticism of what he narrates from Saeed Maqburi, and Ibn Abu Dhib, who is among the most reliable narrators regarding Maqburi, disagreed with him. This is why Daraqutni said in Ilal (8/155), "The statement of Ibn Abu Dhib is closer to being correct."I say, this chain contains someone whose standing is unknown.As for what has been narrated from Abu Saeed Khudri, who said the Messenger of Allah ﷺ said, "No people sit in a gathering without mentioning Allah in it but that it will be a regret for them on the Day of Resurrection, even if they enter Paradise," it appears more likely that attributing it to the musnad of Abu Saeed is a mistake. Nasai narrated it in Amal al-Yawm wal-Layla (409) through Abu Amir, from Shuba, from Sulayman, that is Amash, from Zakwan, that is Abu Salih, from Abu Saeed Khudri, who narrated it. The hadith is known to belong to the musnad of Abu Hurairah, for Abdul-Rahman bin Mahdi narrated it from Shuba with this same isnad and attributed it to the musnad of Abu Hurairah. Likewise, others besides Amash narrated it from Abu Salih, from Abu Hurairah.