It is related in a ḥadīth found in Abū Nuʿaym, Ḥilyat al-awliyāʾ, al-Ṭabarānī, al-Duʿā, and other collections that Abū Dharr said: “I said, ‘O Messenger of Allah, teach me some practice which will bring me nearer to heaven and further from hell.’ He said, ‘When you commmit a wrong, accomplish a good deed, for the good deed brings tenfold goodness in return.’  I then asked, ‘O Messenger of God, is (saying) lā ilāha illā Allāh among the good deeds?’ He said, ‘It is the best of good deeds unlike any other.’    

     And in a ḥadīth found in the Musnad collections of Aḥmad b. Ḥanbal and Bazzar, in Ḥilyat al-awliyāʾof Abū Nuʿaym, and several other standard sources, the Prophet (S) is reported to have said, “Renew your faith.” They said, “O Messenger of Allah, how do we renew our faith?” He answered, “By being abundant in the saying, Lā ilāha illā Allāh.”  

     And in a ḥadīth related in the Sunan collections of Ibn Mājah and al-Tirmidhī, in Shuʿab al-īmān by al-Bayhaqī, and several other sources, Jabir b. ʿAbdallah (R ) reported to have said, “I heard the Prophet (S) say, ‘The most excellent invocation is lā ilāh illā Allāḥ and the most excellent supplication is al-ḥamdu li-lLāh.’” 

     In the first version of the wird, this formula was recited 300 times.