Kumayl Ibn Ziyad Nakha’i was a confidant amongst the companions of Imam Ali Ibn Abi Talib (as) and his son Imam Hasan Mujtaba and this sublime Du'a was first heard from the beautiful, though anguished, voice of Imam Ali (as). This dua has been narrated in Mesbah al-Mutahajjid[1] of Shaykh Tusi, one of the greatest Shia scholars and author of Shia’s two trustworthy jurisprudential books. The book Mesbah al-Mutahajjid is one of the old and reliable sources. Shaykh Abbas Qommi, the author of Mafatih al-Jenan has quoted this supplication from the same book. Therefore, based on the recommendations, this supplication is recited on the night of the 15th of Sha’ban and on the eve of (i.e. evening preceding) every Friday with the intention of seeking divine forgiveness.
This holy supplication is full of pleading, humbleness, and submission to the Almighty Creator. It has both mystical and moral contents and there is nothing contradictory to the religious beliefs of any Islamic sects that may require to be confirmed and authenticated. For this reason, the Wahabis of Saudi Arabia who are strict and rigid do not prevent public and open recitation of this supplication.
Conclusively, this dua is valid and we recommend its recitation.
[1] Tusi, Muhammad bin Hasan, Mesbah al-Mutahajjid, p. 844, Fiqh al-Shi’ah Institute, Beirut, 1411 A.H; Sayyid bin Tavoos, Iqbal al-A’mal, p. 706, Dar al-Kutub al-Islamiyah, Tehran, 1367 (1988).