Jami` at-Tirmidhi 3596

Abu Hurairah narrated that the Messenger of Allah (ﷺ) said:“The Mufarridun have preceded.” They said: “And who are the Mufarridun, O Messenger of Allah (ﷺ)?” He said: “Those who absorb themselves in the remembrance of Allah, and remembrance removed their heavy burdens from them, until they will come on the Day of Judgement being light (in weight of their burdens).”