Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: Al-Juhani submitted: "O Messenger of Allah! You know our situation, and we cannot attend (for the whole of) this month. Tell us about Laylat al-Qadr." The Prophet (peace and blessings be upon him) said: "Attend the last seven nights." He submitted: "I am not able to do that." The Prophet (peace and blessings be upon him) said: "Seek it on the night when seven nights remain, and that is tonight." The narrator says: I submitted: "O Messenger of Allah! Tonight is the twenty-third night, and eight nights still remain." The Prophet (peace and blessings be upon him) said: "It happens like this too; the month falls short, and then seven nights will remain."
Abu Ya'la recorded it. Its chain contains a narrator whom I do not know.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 5048