Musnad Abu Ya'la al-Mawsili 110:154

Zuhayr narrated to us, 'Abbad ibn al-'Awwam narrated to us, from Hilal ibn Khabbab, from 'Ikrimah, from Ibn 'Abbas, that Duba'ah bint al-Zubayr ibn 'Abd al-Muttalib came to the Prophet, peace and blessings of Allah be upon him, and said: "O Messenger of Allah, I intend to perform Hajj, so should I make a condition?" He said: "Yes, make a condition." She said: "What should I say?" He said: "Say: 'Labbayk Allahumma Labbayk (Here I am, O Allah, here I am). My place of exiting Ihram is wherever You restrain me.'"