Musnad Ahmad 25:546

Hassan ibn Musa narrated to us, Zuhayr narrated to us, from Abu Ishaq, from al-Dahhak ibn Muzahim, who said: When Ibn Abbas would recite the Talbiyah, he would say: "Labbayk Allahumma Labbayk, Labbayka la sharika laka Labbayk, inna al-hamda wa al-ni'mata laka wa al-mulk, la sharika lak" (Here I am, O Allah, here I am. Here I am, You have no partner, here I am. Indeed, all praise and grace are Yours, and the dominion; You have no partner). He said: And Ibn Abbas said: "Stop at that, for it is the Talbiyah of the Messenger of Allah, may Allah bless him and grant him peace."