Zirr (b. Hubaish) said:

I said to Ubayy b. Ka'b: Tell me about lailat al-qadr, O Abu al-Mundhir, for our companion (Ibn Mas'ud) was questioned about it, and he said: Anyone who gets up for prayer every night all the year round will hit upon it (i.e. lailat al-qadr). He replied: May Allah have mercy on Abu 'Abd al-Rahman. By Allah, he knew that it was in Ramadan, (Musaddad's version goes) but he disliked that the people should content themselves (with that night alone); or he liked that the people should not content themselves (with the night alone). According to the agreed version: By Allah, it is the twenty-seventh night of Ramadan, without any reservation. I said: How did you know that, Abu al-Mundhir? He replied: By the indication (or sign) of which the Messenger of Allah ﷺ informed us. I asked Zirr: What is the sign ? He replied: The sun rises like a vessel of water in the morning following that night; it has no rays until it rises high up.

حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، وَمُسَدَّدٌ، - الْمَعْنَى - قَالاَ حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ عَاصِمٍ، عَنْ زِرٍّ، قَالَ قُلْتُ لأُبَىِّ بْنِ كَعْبٍ أَخْبِرْنِي عَنْ لَيْلَةِ الْقَدْرِ، يَا أَبَا الْمُنْذِرِ فَإِنَّ صَاحِبَنَا سُئِلَ عَنْهَا . فَقَالَ مَنْ يَقُمِ الْحَوْلَ يُصِبْهَا . فَقَالَ رَحِمَ اللَّهُ أَبَا عَبْدِ الرَّحْمَنِ وَاللَّهِ لَقَدْ عَلِمَ أَنَّهَا فِي رَمَضَانَ - زَادَ مُسَدَّدٌ وَلَكِنْ كَرِهَ أَنْ يَتَّكِلُوا أَوْ أَحَبَّ أَنْ لاَ يَتَّكِلُوا ثُمَّ اتَّفَقَا - وَاللَّهِ إِنَّهَا لَفِي رَمَضَانَ لَيْلَةُ سَبْعٍ وَعِشْرِينَ لاَ يَسْتَثْنِي . قُلْتُ يَا أَبَا الْمُنْذِرِ أَنَّى عَلِمْتَ ذَلِكَ قَالَ بِالآيَةِ الَّتِي أَخْبَرَنَا رَسُولُ اللَّهِ ﷺ . قُلْتُ لِزِرٍّ مَا الآيَةُ قَالَ تُصْبِحُ الشَّمْسُ صَبِيحَةَ تِلْكَ اللَّيْلَةِ مِثْلَ الطَّسْتِ لَيْسَ لَهَا شُعَاعٌ حَتَّى تَرْتَفِعَ .