Hz. Peygamber's most frequent dua was: 'Ya Muqallibal-qulub, thabbit qalbi 'ala dinik' — O Turner of hearts, make my heart firm upon Your religion. Despite being Hz. Peygamber, he frequently asked for steadfastness, showing that no one is safe from deviation without Allah's help.
يَا مُقَلِّبَ الْقُلُوبِ ثَبِّتْ قَلْبِي عَلَى دِينِكَ
Ya Muqallibal-qulub, thabbit qalbi 'ala dinik.
Meaning: O Turner of hearts, make my heart firm upon Your religion.
Source: Sunan al-Tirmidhi #2140This was the most frequent dua of Hz. Peygamber (sallallahu aleyhi ve sellem), despite his exalted rank. If the Messenger of Allah feared for his own heart, how much more should we? The hearts are between Allah's fingers — He turns them as He wills. This dua is an acknowledgment that steadfastness is a gift from Allah, not something we achieve on our own.
يَا مُقَلِّبَ الْقُلُوبِ ثَبِّتْ قَلْبِي عَلَى دِينِكَ
The most frequent supplication of the Prophet (peace be upon him) was: 'Ya Muqallibal-qulub, thabbit qalbi 'ala dinik.' I said: 'O Messenger of Allah, we believe in you and in what you have brought. Do you fear for us?' He said: 'Yes, for the hearts are between two fingers of Allah, He turns them however He wills.'