Messenger of Allah ﷺ said, "The younger person should greet the older one, and the walking person should greet the sitting one, and the small number of persons should greet the large number of persons."  

قَالَ رَسُولُ اللَّهِ ﷺ يُسَلِّمُ الصَّغِيرُ عَلَى الْكَبِيرِ وَالْمَارُّ عَلَى الْقَاعِدِ وَالْقَلِيلُ عَلَى الْكَثِيرِ