From Sahih Muslim (Hadith 6808):
Abu Huraira reported that Allah's Messenger (ﷺ) was travelling along the path leading to Mecca that he happened to pass by a mountain called Jumdan. He said:Proceed on, it is Jumdan, Mufarradun have gone ahead. They (the Companions of the Holy Prophet) said: Allah's Messenger, who are Mufarradun? He said: They are those males and females who remember Allah much
Reference: Muslim 6808