Musnad Abu Ya'la al-Mawsili 122:3

Zuhayr ibn Harb narrated to us, Sufyan ibn 'Uyaynah narrated to us, from Mus'ab, who heard Anas ibn Malik saying: I heard the Prophet, may Allah bless him and grant him peace, pronouncing the intention (ihlal) for Hajj and 'Umrah together.