Lvalio asked me to post the following comment. Apparently he had a problem in posting it. He thinks it is a problem at his end. Anyway, the following is the comment.
None of this (listening to dhammā) is absolutely necessary to accomplish the state of Sotapanna!
Just understand (understand) the true Dhamma (saddhamma) is sufficient.
And how is it necessary that the master, teacher be an Ariya and not only a good person, or a virtuous person, or etc.
But he who teaches the true Dhamma can only be an Ariya (at least one Sotapanna). And how could he teach the real Dhamma if he wasn’t?
Sometimes the person who read and understood the dhammā a little, starts to think about it and suddenly she sees the first noble truth
Only that, seeing the first noble truth is enough to accomplish Sotapanna, because Lord Buddha said that he who sees the 1st immediately sees the other three, because they are the logical consequences of the 1st
“Four Noble Truths – Suffering and Its Elimination.”