Jami` at-Tirmidhi Book 48, Hadith 209
“Supplicate to Allah to heal me.” He (ﷺ) said: “If you wish I will supplicate for you, and if you wish, you can be patient, for that is better for you.” He said: “Then supplicate to Him.” He said: “So he ordered him to perform Wudu’ and to make his Wudu’ complete, and to supplicate with this supplication: ‘O Allah, I ask You and turn towards You by Your Prophet Muhammad (ﷺ), the Prophet of Mercy. Indeed, I have turned to my Lord, by means of You, concerning this need of mine, so that it can be resolved, so O Allah so accept his intercession for me (Allāhumma innī as’aluka wa atawajjahu ilaika binabiyyka Muḥammadin nabi-ir-raḥmati, innī tawajjahtu bika ila rabbī fī ḥājatī hādhihī lituqḍā lī, Allāhumma fashaffi`hu fīyya).’”
“My father narrated to me, from my grandfather, that he heard the Prophet (ﷺ) say: ‘Whoever says: “I seek forgiveness from Allah, the Magnificent, whom there is none worthy of worship but Him, the Living, Al-Qayyum, and I repent to him,” (Astaghfirullāhal-`Aẓīm alladhī lā ilāha illā huwal-Ḥayyul-Qayyūmu wa atūbu ilaih) then Allah will forgive him, even if he fled from battle.’”
`Amr bin `Abasah reported to me that he heard the Prophet (ﷺ) say: “The closest that the Lord is to a worshipper is during the last part of the night, so if you are able to be of those who remember Allah in that hour, then do so.”