Musnad Ahmad 27:250

Yahya narrated to us, from Ubaydullah, from Nafi’, from Ibn Umar, from the Prophet (peace and blessings of Allah be upon him), regarding the verse: {The day when mankind will stand before the Lord of the worlds} [Al-Mutaffifin: 6]. He said: "He will stand in his sweat up to the middle of his ears."