The Prophet ﷺ said, "The young should greet the old, the passer by should greet the sitting one, and the small group of persons should greet the large group of persons. "  

عَنِ النَّبِيِّ ﷺ قَالَ يُسَلِّمُ الصَّغِيرُ عَلَى الْكَبِيرِ وَالْمَارُّ عَلَى الْقَاعِدِ وَالْقَلِيلُ عَلَى الْكَثِيرِ