Mishkat al-Masabih #2442

Ibn ‘Umar said that God’s messenger used to perform two rak’as in Dhul Hulaifa, then when the she-camel stood up with him on its back at the mosque of Dhul Hulaifa, he shouted these words, saying, “Lubbaik, O God, labbaik labbaik wa-sa‘daik ('Always ready to obey.’) ; good is in Thy hands; labbaik; desire and action are directed towards Thee. (Bukhari and Muslim, the wording being Muslim's.) (It is strange to find a tradition from Bukhari and Muslim in section (b). The author has explained in his introduction that section (a) is confined to Bukhari and Muslim and section (b) to other authorities)