Is it permissible to supplicate to Allah by means of one's righteous deeds, such as when the supplicant says, "O Lord of the Worlds, I seek Your mercy that You answer my prayer and accept it from me by virtue of my fasting that I observed for Your noble countenance"?

Asking Allah by virtue of fasting or other good deeds is a legitimate means of seeking intercession with Allah through these actions. Nevertheless, it is preferable for the supplicant to adhere to the supplications found in the Quran and Sunnah (definition), for they encompass all goodness, blessings, and sufficiency. Indeed, the Prophet, peace and blessings be upon him, preferred comprehensive supplications.