The holy QUR'AN gives out the fact that among the apostles of God...
The holy QUR'AN gives out the fact that among the apostles of God, there are grades of superiority of one over the other: "These apostles, We have exalted some of them over the others. Of them are some unto whom God hath spoken" [20:11]. "And some He hath raise in degrees.." [2:253].
9- If the first 'KHALIF' or the Vicegerent of God, was superior to the angels in his personal excellence as to entitle him to the 'SIJDAH' or the prostration of the angels (20:116) the Last or the Chief of the Apostles will naturally be a superior- most excellence. His purity physical and spiritual, will be matchlessly divine among the creation as a whole. Naturally such a super-fine personality can never be succeeded but by those of the same purity.
Referring to the purity of the Last Apostle and the people of his holy House, the AHLUL-BAIT, God had declared: "God only willeth that He keepeth away un-cleanliness from you, O; AHLUL-BAIT, and purify you a thorough purification" [33:33]. God could have purified only the holy Prophet, if the divine guidance to mankind had to end with him. The equal purification of his 'AHLUL-BAIT' along with him can never be purposeless for God is the All-Wise Lord.
The act of the All-Wise can never be purposeless or vain. Thus the equal purification of the 'AHLUL-BAIT' along with the holy Prophet, clearly indicates that the 'AHLUL-BAIT' have also to serve one and the same identical purpose along with holy Prophet and after him, not as apostles but as the 'Imams' OR THE Vicegerents of the Lord on earth.
It is only a matter of simple common sense to know that the place of the pure can be taken only by the pure and no impurity can ever fit in, in the place o purity, perfect and supreme.
10- Every apostle of God was a 'KHALIFATULLAH' or the vicegerent of God, some were for themselves, some for a particular people and some for a particular place and age with particular assignment and jurisdiction: Noah was sent to a particular people 23:23, Moses to the people of Pharaoh 20:24, SALEH to THAMUD 7:73, Lot to his people 7:80 and similarly the others.
11- The Last Apostle or the Chief Vicegerent of God, was sent not to any one people or time, but to mankind as a whole i.e., as long as mankind is there on earth 7:158, 4:79, 34:28.