Yahya related to me from Malik, from Abd ar-Rahman ibn Harmalaal-Aslami, that somebody asked Said ibn al-Musayyab, "Can I do umrabefore I do hajj?", and Said said, "Yes, the Messenger of Allah, mayAllah bless him and grant him peace, did umra before doing hajj."
USC-MSA web (English) reference: Book 20, Hadith 58
Arabic reference: Book 20, Hadith 763