(40) باب فَضْلِ لَيْلَةِ الْقَدْرِ وَالْحَثِّ عَلَى طَلَبِهَا وَبَيَانِ مَحَلِّهَا وَأَرْجَى أَوْقَاتِ طَلَبِهَا
Zirr b. Habaish reported:
I thu asked Ubayy b. Ka'b (Allah be pleased with him): Your brother (in faith) Ibn Mas'ud says: He who stands (for the night prayer) throughout the year would find Lailat-ul-Qadr, whereupon he said: May Allah have mercy upon him; (he said these words) with the intention that people might not rely only (on one night), whereas he knew that it (Lailat-ul-Qadr) is in the month of Ramadan and it is the twenty-seventh night. He then took oath (without making any exception, i. e. without saying In sha Allah) that it was the twenty-seventh night. I said to him: Abu Mundhir, on what ground do you say that? Thereupon he said: By the indication or by the sign which the Messenger of Allah (ﷺ) gave us, and that is that on that day (the sun) would rise without having any ray in it.
Reference: Sahih Muslim 762 d
In-book reference: Book 13, Hadith 283
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2633