Musannaf Ibn Abi Shayba 1:565

Ibn ‘Ulayyah narrated to us, from ‘Ubayd Allah ibn al-’Ayzar, from Talq ibn Habib, who said: ‘Umar ibn al-Khattab saw a man scratching his armpit or touching it, so he said: "Stand up and wash your hands, or purify yourself."