(2) باب دُعَاءِ رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ
It was narrated that Anas bin Malik said:
"The Messenger of Allah (saas) often used to say: 'Allahumma thabbit qalbi 'ala dinika [O Allah, make my heart steadfast in (adhering to) Your religion].' A man said: 'O Messenger of Allah! Do you fear for us when we have believed in you and in (the Message) that you have brought?' He said: 'Hearts are between two of the fingers of the Most Merciful, and He controls them.'" (Hasan)Al-A'mash (one of the narrators) indicated with his fingers.
Reference: Sunan Ibn Majah 3834
In-book reference: Book 34, Hadith 8
English translation: Vol. 5, Book 34, Hadith 3834