Luke 3:22 and the Holy Spirit descended on him in bodily form like a dove. And a voice came from heaven: "You are my Son, whom I love; with you I am well pleased."
I think there are good faith arguments against the Doctrine of the Trinity based on scripture and that one has to study the scriptures and seek heavenly guidance as to how to understand various passages. Clearly a large contingent of Catholic, Orthodox and Prostestant Churches (which, after all, originated in Catholocism) choose to make the doctrine the line in the sand. Others do not agree and I won’t presume to tell this seeker the Trinity is a hard and fast scriptural truth to all non-apostate churches.