Sunan Abi Dawud 5198
سنن أبي داود#5198SahihAbu Hurairah reported the Messenger of Allah (May peace be upon him) as saying :The young should salute the old, the one who is passing by should salute the one who is sitting, and a small company should salute a large one
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
In-book reference: 43:426