What is the difference between a Messenger (Rasul) and one who is sent (Mab’uth)? And was Muhammad (peace be upon him) sent only to his people, and a Messenger to all people through the Quran, such that they are obligated only by the Quran and not by his Sunnah?

The meanings of "ba‘atha" (sent forth/raised up) and "arsala" (sent) converge in directing a person. Both "ba‘atha" and "arsala" denote directing, and the Holy Quran uses both terms to signify the same meaning. However, "ba‘atha" has a broader meaning than "arsala." "Arsala" is more specific to the sending of a prophet to his people and is more frequently used in that context. As for "ba‘atha," it carries wider meanings such as stirring up and bringing to life. There is no difference between saying "Allah ba‘atha Muhammad" (Allah sent forth Muhammad) and "Allah arsala Muhammad" (Allah sent Muhammad). The distinction that the Prophet was "mab‘ooth" (sent forth) to his people and "mursal" (sent) to those who came after them, with the Quran alone sufficing for the latter, is invalid and contrary to religion. For the Prophet was "bu‘itha" (sent forth) and "ursila" (sent) to all people until the Day of Judgment. And whoever comes after the prophethood is obligated to follow the Sunnah and the Quran, for the Sunnah is an elucidation of the Quran, and from it, rulings are understood.