"The Bible does NOT teach this. Where did this assumption of Mary come from? Man's doctrine?"
Same place the Bible did: Catholic tradition.
If you are asking because you are curious read the links. If you are trying to cause a fight, forget about it.
Yep. You could call the doctrine of assumption nothing more than an assumption. Heh.
No clear reference to the assumption of Mary exists before the 6th century, and only then from highly dubious sources. The idea apparently originated with a sect of Egyptian Christians who had been highly influenced by Gnostic traditions. In fact, the earliest reference to the end of Mary's life is from Epiphanius in 377 A.D. He writes that no one knows what happened to Mary:
But if some think us mistaken, let them search the Scriptures. They will not find Mary’s death; they will not find whether she died or did not die; they will not find whether she was buried or was not buried ... Scripture is absolutely silent [on the end of Mary] ... For my own part, I do not dare to speak, but I keep my own thoughts and I practice silence ... The fact is, Scripture has outstripped the human mind and left [this matter] uncertain ... Did she die, we do not know ... Either the holy Virgin died and was buried ... Or she was killed ... Or she remained alive, since nothing is impossible with God and He can do whatever He desires; for her end no-one knows.’ (Epiphanius, Panarion, Haer. 78.10-11, 23. Cited by juniper Carol, O.F.M. ed., Mariology, Vol. II (Milwaukee: Bruce, 1957), pp. 139-40).Here's a good summary on the doctrine:This dogma has no serious connection with the Bible at all, and its defenders scarcely pretend that it has. It cannot honestly be said to have any solid ground in patristic theology either, because it is frist known among Catholic Christians in even its crudest form only at the beginning of the fifth century, and then among Copts in Egypt whose associations with Gnostic heresy are suspiciously strong; indeed it can be shown to be a doctrine which manifestly had its origin among Gnostic heretics. The only argument by which it is defended is that if the Church has at any time believed it and does now believe it, then it must be orthodox, whatever its origins, because the final standard of orthodoxy is what the Church believes. The fact that this belief is presumably supposed to have some basis on historical fact analogous to the belief of all Christians in the resurrection of our Lord makes its registration as a dogma de fide more bewilderingly incomprehensible, for it is wholly devoid of any historical evidence to support it. In short, the latest example of the Roman Catholic theory of doctrinal development appears to be a reductio ad absurdum expressly designed to discredit the whole structure (R.P.C. Hanson, The Bible as a Norm of Faith (University of Durham, 1963), Inaugral Lecture of the Lightfoot Professor of Divinity delivered in the Appleby Lecture Theatre on 12 March, 1963, p. 14).In short, any "doctrine" concerning what happened to Mary is nothing more than sheer speculation.