Shahr ibn Hawshab reported: I asked Umm Salamah (may Allah be pleased with her): "O Mother of the Believers, what was the supplication that the Messenger of Allah (may Allah's peace and blessings be upon him) used to say most frequently when he was with you?" She said: "The supplication he said most frequently was: 'O Turner of the hearts, keep my heart firm upon Your religion!'"
عن شهر بن حوشب قال: قلت لأم سلمة -رضي الله عنها-، يا أم المؤمنين، ما كان أكثر دعاء رسول الله -صلى الله عليه وسلم- إذا كان عندك؟ قالت: كان أكثر دعائه: «يا مقلب القلوب ثبت قلبي على دينك».
شرح الحديث :
"O Turner of the hearts!" i.e. You are the one Who directs them to obedience at times, and to disobedience at others, and to heedfulness at times, and to heedlessness at others. "Keep my heart firm upon Your religion!" i.e. make it steadfast upon Your sound religion, and not swerving from the straight path.