Lailatul-Qadr is one of the last ten nights of the month of Ramadhan. Al-Majlisi, on p. 10, Vol. 94, of his Bihar al-Anwar, quotes Imam Ali ibn Abu Talib (as) saying the following about it: "Seek it in the last ten days, for the mash’ars are seven, and so are the heavens, and the (layers of the) earth, and seven kine, and seven ears of grain."
He (as) is also quoted saying that during those days, the Messenger of Allah (S) used to roll his bed, tie his mantle, and keep his family awake (especially) during the 23rd night, sprinkling water on the faces of those who were overcome by sleep. Fatima al-Zahra (as) used not to permit anyone in her house to sleep, giving them very little to eat (since over-eating causes drowsiness and heaviness), and she used to get ready for it even during daytime.
She (as) used to say, "One who is deprived of its goodness truly suffers the greatest deprivation." It is highly recommended, therefore, to perform ghusul particularly during the last ten days of the month of Ramadhan. According to Al-Iqbal, Abu Abdullah, peace be upon him, is quoted saying that the Messenger of Allah (S) used to have his ghusul each night during the last ten nights of the month of Ramadhan.