Jesus was having a conversation with some people who were having a problem with Him being the Messiah, and He said this to them:
But you do not believe, because you are not of My sheep, as I said to you. My sheep hear My voice, and I know them, and they follow Me. (John 10:26-27)
So, they couldn’t believe because they were not of His sheep? Does that mean they had to become one of His sheep before they could believe?
I think we will find that the reason these people could not believe was because they refused to do so. They had seen plenty of evidence of who Jesus was, but rejected it. Their unwillingness to consider the evidence meant that they couldn’t believe.