وَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " لِيُسَلِّمْ الصَّغِيرُ عَلَى الْكَبِيرِ ، وَالْمَارُّ عَلَى الْقَاعِدِ ، وَالْقَلِيلُ عَلَى الْكَثِيرِ " .
And the Prophet Muhammad (peace be upon him) said: The younger should greet the elder, the one passing by should greet the one sitting, and the smaller group should greet the larger group.