Musnad Ahmad 27:1012

'Attab ibn Ziyad narrated to us, Abu Hamza—meaning al-Sukkari—narrated to us, from Ibrahim—meaning al-Sa'igh—from Nafi', from Ibn 'Umar, who said: "The Messenger of Allah (ﷺ) used to separate the Witr and the Shafa' with a taslim, and he would make us hear it."