Muwatta Imam Malik (Riwayat Ibn al-Qasim)

And with this chain (it is narrated from Sayyiduna Anas bin Malik, may Allah be pleased with him) that in Ramadan, the Messenger of Allah, peace and blessings be upon him, came to us and said: "Tonight (Laylat al-Qadr) was shown to me, until two men argued and it was taken away, so seek it in the ninth, seventh, and fifth (nights)."