It is narrated from Ibn Abbas (may Allah be pleased with them both) that Sayyidah Duba'ah bint al-Zubayr bin Abd al-Muttalib (may Allah be pleased with her) came to the Prophet (peace and blessings be upon him) and said: "O Messenger of Allah! I wish to perform Hajj; may I make a condition?" He (peace and blessings be upon him) said: "Yes." She said: "What should I say?" He (peace and blessings be upon him) said: "Say: 'Labbayk Allahumma labbayk (Here I am, O Allah, here I am); my place of leaving ihram on the earth is wherever You detain me.'"
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21198