Musnad Ahmad 27:1760

'Ali ibn Ishaq narrated to us, 'Abdullah and 'Attab informed us, 'Abdullah narrated to us, Abu al-Sabah al-Ayli informed us, I heard Yazid ibn Abi Sumayyah saying: I heard Ibn 'Umar saying: "Whatever the Messenger of Allah, peace and blessings of Allah be upon him, said regarding the lower garment (izar), it applies to the shirt (qamis)."