“but every spirit that refuses to confess Jesus, that spirit is not from God, and this is the spirit of the antichrist, which you have heard is coming, and now is already in the world.”
1 John 4.3
One test of belonging to God was the teaching about Jesus, his deity and humanity. Whoever denied it (spirit=teaching) was not only wrong, but belong to the present evil forces arrayed against God.
God’s truth is clear. To teach different is to “refuse” to confess Jesus. The truth must be welcomed and obeyed. To what spirit do I belong?