Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) said: I heard the Messenger of Allah (peace and blessings be upon him) saying: "The hearts of the children of Adam are all between two of the fingers of Allah, the Most Merciful, like a single heart; He turns them however He wills." Then the Messenger of Allah (peace and blessings be upon him) said: "'Allahumma musarrif al-qulub, sarrif qalbi ila ta'atik' (O Allah, Turner of hearts, turn my heart to Your obedience)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13676