Musnad Ahmad 30:2303

Qutaybah narrated to us, 'Abd al-'Aziz ibn Muhammad narrated to us, from Thawr, from Abu al-Ghayth, from Abu Hurayrah, that the Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, the sweat on the Day of Resurrection will go into the earth seventy arm-spans, and it will reach the mouths of the people, or to their ears." Thawr was in doubt as to which of the two he said.