Hadith 166

Bulugh al-Maram

Book 2: The Book of Prayer
وَعَلَى هَذَا يُحْمَلُ اَلنَّفْيُ فِي رِوَايَةِ مُسْلِمٍ , خِلَافًا لِمَنْ أَعَلَّهَا.‏ 1‏ ‏‏.‏
The negation (of recitation of the Bismillah) in the report of Muslim can be understood in light of this report (i.e. it was recited silently), as opposed to those who declared Muslim's report as being defective.