Is it permissible to supplicate to Allah by means of a righteous deed whose acceptance is uncertain, and in the absence of an accepted deed, to supplicate by means of His vast mercy?

Seeking intercession through righteous deeds is permissible, but what is authentically reported in the Sunnah is seeking intercession through a known and specific deed, as in the hadith of the three men in the cave. As for the second part of the supplication, which is the supplicant's saying: "For Your mercy is dearer and more expansive to me," it is a permissible form of seeking intercession through Allah's names and attributes. Some may object to combining the two, arguing that if His mercy is more expansive and dearer, there is no need to present the possibility of an accepted deed. Sufficing with seeking intercession through Allah's mercy is present in the Sunnah, such as in the hadith: "O Allah, Your forgiveness is more expansive than my sins, and Your mercy is more hopeful to me than my deeds." It is better to restrict oneself to what is authentically reported in the Sunnah, either seeking intercession through a specific righteous deed or seeking intercession through Allah's names and attributes.