Zirr says: I asked Ubayy ibn Ka'b (may Allah be pleased with him) to tell me about Laylat al-Qadr, because your brother Abdullah ibn Mas'ud (may Allah be pleased with him) says that whoever stands in prayer throughout the year can attain Laylat al-Qadr? Ubayy (may Allah be pleased with him) replied: May Allah's mercy be upon him, he knows that Laylat al-Qadr is in the month of Ramadan and it is on the twenty-seventh night, but he wants to keep it hidden from the people so that they do not rely on it and become complacent. Then he swore by the One who sent down the Book upon Muhammad (peace be upon him), that Laylat al-Qadr is on the twenty-seventh night of Ramadan. I asked: O Abu al-Mundhir! How do you know this? He replied: By the sign that has been told to us, that on the morning following that night, when the sun rises, it has no rays.