From Sahih Muslim (Hadith 3010):
Ibn 'Abbas (Allah be pleased with them) 'is reported to have said:The Messenger of Allah (ﷺ) put on Ihigm for Hajj. When four days of Dhu'l-Hijja were over, he led the dawn prayer, and when the prayer was complete, he said: He who wants to change it to Umra may do so
Reference: Muslim 3010