Is repeating the greeting of peace upon the deceased three times from the Sunnah, and what is most preferable in that regard, and what is the meaning of Ibn Muflih's statement, "Its repetition was reported among the Muhajirin"?

The primary rule regarding greeting the deceased is to restrict oneself to what has been authentically reported from the Messenger of Allah, peace and blessings be upon him, which is his saying: "Peace be upon you, O inhabitants of the dwellings, from among the believers and Muslims. And verily, Allah willing, we shall join you. I ask Allah for well-being for us and for you." As for greeting three times, it is an opinion held by Abdullah ibn Umar, and it is not to be given precedence over what is authentically reported from the Prophet, peace and blessings be upon him.