Sayyiduna Anas (may Allah be pleased with him) said: A time limit was set for us for trimming the moustache, clipping the nails, plucking the armpit hair and shaving the pubic hair, that we "should not leave them for more than forty days."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 691