From Sahih Muslim (Hadith 2946):
Jabir b. 'Abdullah (Allah be pleased with them) reported:We set out with Allah's Messenger (ﷺ) as Muhrim for Hajj. The Messenger of Allah (ﷺ) commanded us to make this Ihram for Umra, and some put it off (after performing 'Umra), but the Prophet (ﷺ) had sacrificial animals with him, so he could not make it (this Ihram) as that of Umra
Reference: Muslim 2946