Virtues of Dhikr

Qur'an states:

يَا أَيُّهَا الَّذِينَ آمَنُوا اذْكُرُوا اللَّهَ ذِكْرًا كَثِيرًا

Translation: O you who Believe, make abundant remembrance of ALLAH!" (33:41)

In Tafsir of this verse Imam al-Qurtubi (rah) mentions the hadith:

وروى أبو سعيد عن النبيّ صلى الله عليه وسلّم: «أكثروا ذكر الله حتى يقولوا مجنون

Translation: Abu Sa'eed al Khudri (ra) narrates from the Prophet (Peace be upon him) who said: Do Dhikr so much that people start calling you Majnoon (mad) [Tafsir ul Qurtubi, Volume No. 14, Page No. 197]

This hadith is narrated in Musnad Ahmed (3/67, 81). Ibn Hibban in his “SAHIHA” (#814). Imam al-Hakim in his Mustadrak ala Sahihayn (1/499)

عَنْ أَبِي مُوسَى رضي الله عنه قَالَ: قَالَ النَّبِيُّ صلي الله عليه وآله وسلم: مَثَلُ الَّذِي يَذْكُرُ رَبَّهُ وَالَّذِي لَا يَذْكُرُ رَبَّهُ مَثَلُ الْحَيِّ وَالْمَيِّتِ

Translation: Abu Musa (رضی اللہ عنہ) narrates that the Holy Prophet (صلی اللہ علیہ وآلہ وسلم) said, “He who remembers his Lord and he who does not are like the living and the dead.”

Bukhari, as-Sahih (5:2353#6044)