Musannaf Ibn Abi Shayba 1:1457

Abu Khalid—and he is not al-Ahmar—narrated to us, from Hisham, from Yahya ibn Abi Kathir, from ‘Awn ibn ‘Abd Allah ibn ‘Utbah and al-Zuhri, they both said: "If a man touches his armpit, he must repeat the ablution."