This excerpt is taken from Professor Dr. Fazl Elahi's book Masael-e-Qurbani.
The prescribed method is that while slaughtering the sacrificial animal, one should say [Bismillah Wallahu Akbar]. It has already been mentioned in the hadith narrated by Hazrat Anas (may Allah be pleased with him) reported by Imam Bukhari and Imam Muslim that
The Holy Prophet (peace be upon him) sacrificed two rams with large horns. He slaughtered both with his own hands and said [Bismillah Wallahu Akbar] while slaughtering.
For the reference of the hadith, see: this book
Reference: p. 37
