ibn Mas'ud · Chapters on Seeking Permission

from Abu Hurairah that the Prophet (ﷺ) said: "The rider gives the Salam to the walking person, and the walking person to the sitting person and the few to the many." Ibn Al-Muthanna added in his narration: "And the young one gives the Salam to the elder."

that he asked Anas bin Malik: "Did the Companions of the Messenger of Allah (ﷺ) use to shake each other's hand?" He said, "Yes."