Kumayl ibn Ziyad Nakha'i, a confidant of Ali ibn Abi Talib, had attended an assembly in the Mosque at Basra which was addressed by Imam Ali in the course of which the night of the 15th of Sha'aban was mentioned.

Ali ibn Abu Talib is claimed to have said:

"Whosoever keeps awake in devoutness on this night and recites the Du'a of Prophet Khidhr, undoubtedly that person's supplication will be responded to and granted."
When the assembly at the Mosque had dispersed, Kumayl called at the house where Ali was staying, and requested him to acquaint him with Prophet Khidhr's supplication. Ali asked Kumayl to sit down, record and memorise the du'a which he dictated to Kumayl.

Ali then advised Kumayl ibn Ziyad Nakha'i to recite this du'a on the eve of (i.e. evening preceding) every Friday, or once a month or at least once in every year so that, added Ali, "Allah may protect thee from the evils of the enemies and the plots contrived by impostors. O' Kumayl! in consideration of thy companionship and understanding, I grant thee this honour of entrusting this du'a to thee."