(39) باب اسْتِحْبَابِ صَوْمِ سِتَّةِ أَيَّامٍ مِنْ شَوَّالٍ اتِّبَاعًا لِرَمَضَانَ
Abu Ayyub reported a hadith like this (through another chain of transmitters).
Reference: Sahih Muslim 1164 c
In-book reference: Book 13, Hadith 266
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2616