How sound is the Hadith attributed to the Prophet—may God’s prayers and peace be upon him—to Ali: "You are to me as Aaron was to Moses," and is it permissible to supplicate with "O God, bless me in death and what comes after death," which is mentioned therein, and to act upon the supplications and deeds contained within it?

The majority of the exhortations attributed to Ali (may Allah be pleased with him) are fabricated and it is impermissible to act upon them or to take them as a source of knowledge, with the exception of the hadith: "You are to me as Aaron was to Moses." As for the supplication: "O Allah, bless me in death and what comes after death," it is extremely weak and is attributed to Sufyan al-Thawri. It is permissible to supplicate with it occasionally to seek blessings in death and what comes after it, but it is better to suffice with the supplications established in the Quran and Sunnah.