The دعاء for sacrifice is: 'Bismillahi wallahu Akbar, Allahumma minka wa lak, Allahumma taqabbal minni' — In the name of Allah, Allah is the Greatest, O Allah this is from You and for You, O Allah accept from me. The animal must be slaughtered facing the القبلةh while saying Bismillah and Allahu Akbar.
بِسْمِ اللَّهِ وَاللَّهُ أَكْبَرُ، اللَّهُمَّ مِنْكَ وَلَكَ، اللَّهُمَّ تَقَبَّلْ مِنِّي
Bismillahi wallahu Akbar, Allahumma minka wa lak, Allahumma taqabbal minni.
Meaning: In the name of Allah, Allah is the Greatest. O Allah, this is from You and for You. O Allah, accept from me.
Source: Sunan Abu Dawud #2810The sacrifice during الحج follows the tradition of Prophet Ibrahim (صلى الله عليه وسلم), who was ready to sacrifice his son Isma'il in obedience to Allah's command. Allah says: 'It is neither their meat nor their blood that reaches Allah, but it is your piety that reaches Him' (القرآن 22:37). The act of sacrifice is about submission to Allah's will and sharing blessings with the poor.
بِسْمِ اللَّهِ وَاللَّهُ أَكْبَرُ، اللَّهُمَّ مِنْكَ وَلَكَ، اللَّهُمَّ تَقَبَّلْ مِنِّي
The Prophet (peace be upon him) slaughtered his sacrifice on the Day of Eid, saying: 'Bismillahi wallahu Akbar, Allahumma hadha 'anni wa 'amman lam yudahhi min ummati' — In the name of Allah, Allah is the Greatest, O Allah this is on my behalf and on behalf of those of my ummah who did not sacrifice.