Are the greetings in the prayer from God or from the Messenger?

The Messenger, peace and blessings be upon him, does not legislate of his own accord; rather, it is revelation from Allah, as He states: "Nor does he speak of (his own) desire. It is only an inspiration inspired." And obedience to him is obedience to Allah, as He states: "He who obeys the Messenger has obeyed Allah." Therefore, what the Messenger legislated concerning the Tashahhud in prayer is from Allah. And the Tashahhud is legislated by the Sunnah, not by the Quran.