Hadith: The Prophet (may Allah's peace and blessings be upon him) used to say between the two prostrations: O Allah, forgive me, have mercy on me, grant me wellness and safety, guide me and provide for me

عن ابن عباس رضي الله عنهما أن النبي صلى الله عليه وسلم كان يقول بين السَّجدتَين: «اللَّهمَّ اغْفِرْ لي، وارْحَمْنِي، وعافِني، واهْدِني، وارزقْنِي».
[صحيح] - [رواه أبو داود]

Ibn ‘Abbās (may Allah be pleased with him) reported: The Prophet (may Allah's peace and blessings be upon him) used to say between the two prostrations: "O Allah, forgive me, have mercy on me, grant me wellness and safety, guide me and provide for me."
Sahih/Authentic. - [Ibn Maajah]

Explanation

Ibn ‘Abbās (may Allah be pleased with him) told us that the Prophet (may Allah's peace and blessings be upon him): "used to say between the two prostrations: ‘O Allah, forgive me…’ meaning: he used to say that supplication between the two prostrations - and there is no difference between the obligatory and voluntary prayer here, as all prayers are Dhikr and recitation of the Qur'an. The meaning of "O Allah, forgive me…" is cover me and pardon me without any blame. The meaning of "…have mercy on me…" is give me some of Your Mercy, including covering my faults, sparing me the blame, and bestowing on me the benefits of this world and the Hereafter. "Grant me wellness and safety…" meaning: grant me safety in my religion from sins and malicious allegations, in my body from illnesses and diseases, and in my mind from idiocy and insanity. The most serious diseases are those of the heart that are caused by misguiding allegations or destructive desires. "Guide me…" There are two types of guidance: 1. Guidance to the path of the truth, and this happens to the Muslim and the disbeliever: {And as for Thamūd, We guided them.} [Sūrat Fussilat: 17] meaning: We guided them to the truth. 2. Guidance to success and acceptance. This only occurs to the people of faith, and that is what is intended here. Its meaning: guide me to the truth and make me firm on it. "Provide for me…" meaning: give me sustenance that will free me from the need of any being from Your creatures, and provide me with an expansive provision in the Hereafter, similar to what You have prepared for Your slaves whom You have favored.