"There is no might and no power except with Allah." (1)
This hadith is hasan gharib.

Chapter 96
3831 - Abu Musa al-Ansari narrated to us, saying: Mu'adh ibn Mu'adh narrated to us, from Abu Ka'b, the companion of silk, who said: Shahr ibn Hawshab narrated to me, saying:
I said to Umm Salamah: "O Mother of the Believers, what was the most frequent supplication of the Messenger of Allah, peace and blessings be upon him, when he was with you?" She said: "His most frequent supplication was: 'O Turner of hearts, make my heart firm upon Your religion.'" She said: So I said: "O Messenger of Allah, why is your most frequent supplication 'O Turner of hearts, make my heart firm upon Your religion'?" He said: "O Umm Salamah, there is no human being except that his heart is between two fingers of the fingers of Allah; whomever He wills, He makes firm, and whomever He wills, He causes to deviate." (2)
--------------------------------------------
(1) Weak chain of transmission; 'Abd al-Rahman ibn Sabit did not hear from Abu Umamah al-Bahili according to what Ibn Ma'in and Ibn al-Qattan al-Fasi said, and Layth ibn Abi Sulaym is weak with poor memory.
It was also recorded by al-Bukhari in "Al-Adab al-Mufrad" (679), and by al-Tabarani in "Al-Kabir" (7791), and in "Musnad al-Shamiyyin" (2278) via the path of Mu'tamir ibn Sulayman, from Layth, from Thabit ibn 'Ajlan, from Abu 'Abd al-Rahman al-Qasim, from Abu Umamah. It also contains Layth ibn Abi Sulaym, who is weak as previously mentioned.
(2) The hadith is authentic with its supporting witnesses, but this chain of transmission is weak due to the weakness of Shahr ibn Hawshab. It is in "Musnad Ahmad" in both extended and abridged forms under numbers (26519), (26576), and (26679).
It has a supporting witness from the hadith of 'Abdullah ibn 'Amr in Ahmad under number (6569), and it is in =