Hadithcore
Bulugh al-Maram, 68

and Muslim admitted that he dropped this addition deliberately.

وَأَشَارَ مُسْلِمٌ إِلَى أَنَّهُ حَذَفَهَا عَمْدً ا [1]‏ .‏

References2 variants
In-Book Reference
Book 1, Hadith 81
English Reference
Book 1, Hadith 74