Said while making the sacrifice himself
He put his foot on its side and said it as he did it.
بِاسْمِ اللَّهِ اللَّهُمَّ تَقَبَّلْ مِنْ مُحَمَّدٍ وَآلِ مُحَمَّدٍ وَمِنْ أُمَّةِ مُحَمَّدٍ
Bismillāh, Allāhumma taqabbal min Muḥammadin wa āli Muḥammadin wa min ummati Muḥammad.
“In the name of Allah. O Allah, accept from Muhammad, and from the family of Muhammad, and from the nation of Muhammad.”
He included the whole community in his own sacrifice.
The full narration
A'isha reported that Allah's Messenger (ﷺ) commanded that a ram with black legs, black belly and black (circles) round the eyes should be brought to him, so that he should sacrifice it. He said to 'A'isha:Give me the large knife, and then said: Sharpen it on a stone. She did that. He then took it (the knife) and then the ram; he placed it on the ground and then sacrificed it, saying: Bismillah, Allah-humma Taqabbal min Muhammadin wa Al-i-Muhammadin, wa min Ummati Muhammadin (In the name of Allah," O Allah, accept [this sacrifice] on behalf of Muhammad and the family of Muhammad and the Umma of Muhammad
Source
Ṣaḥīḥ Muslim · 5091
- Agreed upon as authentic (al-Bukhārī / Muslim)