Musannaf Ibn Abi Shayba 1:1794

Abu Bakr narrated to us, he said: Abu Khalid al-Ahmar narrated to us, from Usama bin Zayd, from Salih bin Kaysan, that Ubadah bin al-Samit and the companions of the Messenger of Allah (ﷺ) used to go out while the siwak (tooth stick) was upon their ears.