Abdullah ibn Amr reported: The Messenger of Allah, peace and blessings be upon him, said, “Verily, the hearts of the children of Adam, all of them, are between the two fingers of the Most Merciful as one heart. He directs them wherever he wills.” Then the Prophet said, “O Allah, the turner of the hearts, turn our hearts to your obedience.”

Source: Sahih Muslim 2654

Grade: Sahih (authentic) according to Muslim

عَبْدَ اللَّهِ بْنَ عَمْرِو بْنِ الْعَاصِ يَقُولُ أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ إِنَّ قُلُوبَ بَنِي آدَمَ كُلَّهَا بَيْنَ إِصْبَعَيْنِ مِنْ أَصَابِعِ الرَّحْمَنِ كَقَلْبٍ وَاحِدٍ يُصَرِّفُهُ حَيْثُ يَشَاءُ ثُمَّ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ اللَّهُمَّ مُصَرِّفَ الْقُلُوبِ صَرِّفْ قُلُوبَنَا عَلَى طَاعَتِكَ

2654 صحيح مسلم كِتَاب الْقَدَرِ بَاب تَصْرِيفِ اللَّهِ تَعَالَى الْقُلُوبَ كَيْفَ شَاءَ

http://dailyhadith.abuaminaelias.com/2011/05/09/the-hearts-are-between-the-fingers-of-the-most-merciful/