(Imām Bukhārī narrates): Abul Yaman narrated the hadeeth to us, he said: Shu'aib informed us, from Az-Zuhri, he said: Ali bin Husain narrated the hadeeth to me, from Al-Musawwar bin Makhramah, he said that
the Messenger of Allāh صلى الله عليه وسلم stood up, so when he recited the kalimah of shahadah, I heard him saying: "Amma ba'd" (after the shahadah).
Zubaidi has corroborated Shu'aib, from Az-Zuhri.
حَدَّثَنَا أَبُو اليَمَانِ، قَالَ أَخْبَرَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، قَالَ حَدَّثَنِي عَليُّ بْنُ حُسَيْنٍ، عَنِ المِسْوَرِ بْنِ مَخْرَمَة، قَالَ
قَامَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، فَسَمِعْتُهُ حِينَ تَشَهَّدَ يَقول: أَمَّا بَعْدُ
Reference: Sahih Al Bukhari 926