Anas (RA) said that the Prophet (ﷺ) placed his feet on the two jaws of a goat with white and black horns and sacrificed him saying Bismillahi wAllahu akbar.

بِسْمِ اللَّهِ وَاللَّهُ أَكْبَرُ

Bismillaahi wAllahu 'Akbar

With the Name of Allah, Allah is the Most Great!

Reference: Bukhari: 5565