Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: "The Messenger of Allah (peace and blessings be upon him) entered ihram for Hajj. When he reached Makkah, he performed tawaf of the House and (sa'i) between Safa and Marwah. Whoever had entered ihram with a sacrificial animal neither trimmed his hair nor came out of ihram, and he ordered those who had not brought a sacrificial animal to perform tawaf, to perform sa'i, and to trim or shave their hair, and then to come out of ihram."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11072