Praise be to Allah,
Hushaym narrated to us from Yahyaa ibn Abee Ishaaq, ‘Abdul-‘Azeez ibn Suhayb and Humayd at-Taweel who said they had heard Anas ibn Maalik say,
“I heard Allah’s Messenger (peace and blessings be on him) recite the Talbiyah with the intention of performing Hajj and Umrah together,’ saying, ‘Labbayka Umratan wa hajjan, Labbayka umratan wa hajjan.'”
(Musnad Ahmad, Vol. 3, p. 99. The isnaad of this hadeeth is Saheeh. according to the conditions set by al-Bukhaaree and Muslim.)
One of the formulas to recite for performing this kind of Hajj (known as qiran) is Labbayka ‘umratan wa hajjan, (Here I come to You, 0 Allah, for Hajj and ‘Umrah.
Source:
Thulaathiyyaat Musnad Ahmad ibn Hanbal (may Allah have mercy on him)
Reports of Imaam Ahmad that have only three narrators between him and the Prophet, peace, and blessings be upon him.
Shaykh Muhammad ibn Ahmad ibn Saalim as–Saffaareenee al–Hanbalee ~(1114 –1188 AH)