Musnad Ahmad 27:374

Rawh and ‘Affan narrated to us, they said: Hammad ibn Salamah narrated to us, from Humayd. ‘Affan said in his narration: Humayd informed us, from Bakr ibn ‘Abdullah, from Ibn ‘Umar, that he said: The Messenger of Allah (peace and blessings of Allah be upon him) arrived in Makkah, and his companions were reciting the Talbiyah—‘Affan said in his narration: were entering into the state of Ihram—for Hajj. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever wishes to make it an ‘Umrah, let him do so, except for those who have the sacrificial animal with them." They said: "O Messenger of Allah, shall one of us go to Mina while his private part is dripping with semen?" He said: "Yes." The incense burners were lit, and ‘Ali ibn Abi Talib arrived from Yemen. The Messenger of Allah (peace and blessings of Allah be upon him) said: "With what did you enter into Ihram?" He said: "I entered into Ihram with what the Prophet (peace and blessings of Allah be upon him) entered into Ihram." Rawh said: "Then you have a sacrificial animal with us." Humayd said: I narrated this to Tawus, and he said: "That is what the people did." ‘Affan said: "Make it an ‘Umrah."