Or is it the 21st or the 23rd? Al-Husain ibn 'Ubaydullah according to Majalis al-Shaykh, as quoted on p. 2, Vol. 94, of Bihar al-Anwar, quotes Ahmed ibn Muhammad ibn Yahya who in turn quotes his father saying, "I was in the company of Abu Abdullah (as) when Abu Busayr asked him, 'Which night is the one when one is to plead to his Lord whatever he wishes to plead?' The Imam (as) answered him by saying, 'Either the twenty-first or the twenty-third.' He then asked him (as), 'What if I have no strength to observe both of them?' The Imam (as) said, 'How easy it is to observe them when compared to your pleas!"' Abu Abdullah (as) is also quoted in the same volume of Bihar al-Anwar saying, "The twenty-third night of the month of Ramadan is the one when every weighty matter is decided, when trials, tribulations, deaths, and means of sustenance and other matters are determined, and so will whatever Allah decrees to take place for the entire next year; so, congratulations to anyone who remains awake during it bowing, prostrating, contemplating upon his sins, weeping on their account, for if you do all of that, God willing, you Will never be disappointed." Then he added, "Allah will order an angel to call out during each and every day of the month of Ramadan conveying Allah's message to them thus: ' Good news, O My servants f I have forgiven your past sins and permitted some of you to intercede on behalf of the rest on Lailatul-Qadr except those who break their fast with an intoxicant or those who bear grudge against another Muslim brother!"' It is narrated that Allah Subhanahu wa Ta'ala wards off evil and sins and all types of trials on the 25th night from all His servants who fast and grants them light in their hearing and vision; Paradise is decorated during Lailatul-Qadr's day and night.
The great Sunni scholar Ibn Abul-Hadid, in his commentary on Nahjul Balagha, cites Ibn Durayd's Amali stating that al-Jarmoothi quotes Ibn al-Muhallabi quoting Ibn al-Kalbi quoting Shaddad ibn Ibrahim quoting 'Ubaydullah ibn al-Hassan al-Fahri quoting Ibn 'Aradah saying, "The Commander of the Faithful (as) was once asked about Lailatul-Qadr, and he said, 'It is not at all improbable that I know which night it is and deliberately hide such knowledge, and I do not at all doubt that Allah hid such knowledge from you only out of His love for you, for if you knew which night it is, you would have honored it and left the others, and I hope you will not err in its regard."