Musannaf Ibn Abi Shayba 3:4387

Waki’ narrated to us, from Shu’bah, from Ibrahim ibn Muhammad ibn al-Muntashir, from his father, from ‘Amr ibn Sharhabil, who said: ‘Abdullah was asked about the Witr [prayer] after the Adhan, and he said: "Yes, and after the Iqamah."