Silsilat al-Ahadith al-Sahihah

Shahr bin Hawshab says that I asked Sayyida Umm Salamah (may Allah be pleased with her): O Mother of the Believers! When the Messenger of Allah (peace and blessings be upon him) was with you, which supplication did he recite most frequently? She said: He (peace and blessings be upon him) used to recite this supplication most often: "O Turner of the hearts! Keep my heart firm upon Your religion." When he (peace and blessings be upon him) was asked about the reason for this supplication, he (peace and blessings be upon him) said: "The heart of every person is between two fingers from among the fingers of Allah, (He wills that) whomever He wishes, He keeps steadfast (on the right path), and whomever He wishes, He lets go astray."