Mujahid (may Allah have mercy on him) says regarding the saying of Allah Almighty, "And We raised high for you your remembrance" [Surah al-Sharh: 4]: (Allah says:) I am not mentioned except that you are mentioned along with Me: 'Ashhadu an la ilaha illallah, wa ashhadu anna Muhammadan rasulullah' (I bear witness that there is no god but Allah, and I bear witness that Muhammad is the Messenger of Allah).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5771
Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Whenever a people sit in a gathering in which they do not remember their Lord and do not send blessings upon their Prophet (peace and blessings be upon him), it will be a cause of regret for them on the Day of Resurrection; if Allah wills He will take them to account, and if He wills He will forgive them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5772