كتاب مناسك الحج
Read the English translation first, with the original Arabic directly underneath.
It was narrated that Abu Hurairah said:
"Part of the Talbiyah of the Messenger of Allah was: 'Labbaika ilahal-haqq (Here I am, O God of truth)." (Sahih) Abu 'Abdur-Rahman (An-Nasa'i) said: I do not know of anyone who narrated a chain for this from 'Abdullah bin Al-Fadl except for 'Abdul-Aziz. Ismail bin Umayyah reported it from him in Mursal form.
لَبَّيْكَ إِلَهَ الْحَقِّ