Muwatta Malik
Book 20, Hadith 147
Arabic hadith text
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ إِذَا طَعَنَ فِي سَنَامِ هَدْيِهِ وَهُوَ يُشْعِرُهُ قَالَ بِسْمِ اللَّهِ وَاللَّهُ أَكْبَرُ .
Translation
Yahya related to me from Malik from Nafi that Abdullah ibn Umarsaid, when nicking the hump of his sacrificial animal to brand it, "Inthe name of Allah, and Allah is greater."