Abu 'Imran al-Jauni عبد الملك بن حبيب أبو عمران الجوني · The Book of Purification

"A time limit was set for us, by the Messenger of Allah (ﷺ), regarding trimming the mustache, clipping the nails and plucking the pubes; we were not to leave that for more than forty days," on one occasion he said: "Forty nights."