Musnad Ahmad 1101:6

Ali ibn Ishaq narrated to us, Ibn al-Mubarak narrated to us, from Abd al-Rahman ibn Yazid ibn Jabir, Salim ibn Amir narrated to me, al-Miqdad, the companion of the Messenger of Allah (may Allah bless him and grant him peace), narrated to me, saying: I heard the Messenger of Allah (may Allah bless him and grant him peace) saying: "When the Day of Resurrection comes, the sun will be brought near to the servants until it is the distance of a mile or two miles." He said: "The sun will melt them, and they will be in sweat according to the measure of their deeds. Among them is he whom it reaches up to his heels, and among them is he whom it reaches up to his knees, and among them is he whom it reaches up to his waist, and among them is he whom it bridles completely."