Riyad as-Salihin, Book 1, Hadith 604 (In-Book) ⓘ
Anas (May Allah be pleased with him) passed by some children and greeted them (by saying As-salamu 'alaikum to them). Then he said: The Prophet used to do the same.[Al-Bukhari and Muslim].
وعن أنس رضي الله عنه أنه مر على صبيان فسلم عليهم وقال: كان النبي صلى الله عليه وسلم يفعله. ((متفق عليه))