Sahih Muslim Book 7, Hadith Number 2845.

Chapter : Ifrad and Qiran (combining Hajj and Umra in one Ihram) in the performance of pilgrimage.

Bakr b. ‘Abdullah reported: Anas (Allah be pleased with him) had narrated to us that he saw Allah’s Apostle (may peace be upon him) combining Hajj and ‘Umra. He (Bakr) said: I asked (about it) from Ibn ‘Umar, whereupon he said: We entered into the state of Ihram for Hajj (only). I came to Anas and told him what Ibn Umar had said, whereupon he remarked: (You are treating us) as if we were children.