Was the Prophet Muhammad (peace be upon him) an Arab or a Musta'rib, and what is the evidence for that?

The Prophet, peace and blessings be upon him, was from the Arabized Arabs (al-Arab al-Musta'ribah), who are descendants of Ishmael, son of Abraham, the Beloved (Khalil), upon whom be peace. Ishmael was the first to speak eloquent Arabic.

The Arabized Arabs are the Arabs of the Hijaz. It has been established in authentic hadiths that the Prophet, peace and blessings be upon him, was a descendant of Ishmael, as he said: "Indeed, Allah chose Kinanah from the descendants of Ishmael, and He chose Quraysh from Kinanah, and He chose Banu Hashim from Quraysh, and He chose me from Banu Hashim."