And then shall he send his angels, and shall gather together his elect from the four winds, from the uttermost part of the earth to the uttermost part of heaven. Mark 13:27
That God has chosen certain people to be His, before the world was made, is easily proven from multiple scriptures. Yet it is considered a "controversial" doctrine, and one which can get you hated and yelled at. For not only does the Bible plainly say that some people are chosen to be saved, but that some were created to be destroyed.
Let me make it very simple. One chapter of one book can do these things very nicely. That would be chapter nine of Romans. In extreme cases one could even look up two words in an exhaustive concordance--"elect", and "election". Online, it will take less than a minute. You would find every mention of the two words in context. I have just done this before my present writing.
Bible study can often be so easy, yet so few will do it. They would rather rely on church teaching, or just get angry, which comes naturally.
This doctrine really stirs up the flesh as few others will. It takes self, or ego, entirely out of the picture. It makes our origin and destiny a matter of God's will, not ours. Once understood, it is a source of peace like no other.