Mujahid (may Allah have mercy on him) narrates that once the Prophet (peace and blessings be upon him) mentioned a man from the Children of Israel: "He bore arms in the path of Allah for a thousand months." The narrator says that the Companions (may Allah be pleased with them) marvelled at this, so Allah Almighty revealed this (surah): "Indeed, We sent it down on the Night of Decree (Laylat al-Qadr). And what will make you know what the Night of Decree is? The Night of Decree is better than a thousand months" [Surah al-Qadr: 1-3], that is, the thousand months in which that man bore arms in the path of Allah.
This report is mursal.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8522