It is better to cut the nails after seven days. And must be cut once in forty days. Nails cannot be kept large after spending forty days in any order. Narrated from Anas Ibn Malik. " We have a forty-day deadline to cut the sprain , clean the hair below the navel , pull out the armpit hair and cut the nails," he said. Let's not give up too much time. [Sunan Ibn Majah , Chapter: 1 / Purity and its Sunnahs , Hadith Number: 295 Muslim: 256, Nasai: 14 , Abu Dawood: 4200, Maneh of Hadith : Sahih.]