(39) The Book of Greetings
كتاب السلام
(5) Chapter: It Is Recommended To Greet Children With Salam
(5) باب اسْتِحْبَابِ السَّلاَمِ عَلَى الصِّبْيَانِ ‏‏
Sahih Muslim 2168 b 

This hadith has been narrated on the authority of Sayyar with the same chain of transmitters.

وَحَدَّثَنِيهِ إِسْمَاعِيلُ بْنُ سَالِمٍ، أَخْبَرَنَا هُشَيْمٌ، أَخْبَرَنَا سَيَّارٌ، بِهَذَا الإِسْنَادِ ‏.‏
Reference : Sahih Muslim 2168b
In-book reference : Book 39, Hadith 19
USC-MSA web (English) reference : Book 26, Hadith 5391
  (deprecated numbering scheme)