It is narrated from Sayyiduna Ubadah bin Samit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) came out to inform the noble companions (may Allah be pleased with them) about Laylat al-Qadr. Two men began to quarrel, so the Messenger of Allah (peace and blessings be upon him) later said: "I came out to inform you about Laylat al-Qadr, but so-and-so were arguing. Perhaps there is good for you in this. Seek it on the twenty-ninth, twenty-seventh, and twenty-fifth nights."
Hadith Referenceالسنن المأثورة / باب صيام من أصبح جنبا / 322
Hadith Takhrijصحیح بخاری، الایمان، باب خوف المؤمن من أن يحبط عمله وهو لا يشعر ، رقم : 49