Musnad Ahmad 27:166

Yahya narrated to us, from Ubaydullah, Nafi’ narrated to me, 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 will stand in his sweat up to the middle of his ears."