What is the ruling on growing out one's fingernails?

Trimming nails is a Sunnah from the practices of fitra (innate disposition) for both men and women. The majority of scholars do not specify a particular time for cutting them; rather, it depends on necessity and varies from person to person. It has been reported in Sahih Muslim that nails should not be left for more than forty nights. The majority of scholars understood this as being recommended and desirable, while some scholars considered it prohibited, meaning it is not permissible to exceed forty nights.