It has to be biblical. I couldn’t agree more. But this statement from a speaker doesn’t mean you will always get the truth. They could still be espousing erroneous theology.
What you need to watch out for or indications of errant doctrine:
The word doesn’t mean what you think it means. In Greek or Hebrew it actually means this. Or simply it doesn’t mean what you think it means, it means what I’m about to tell you. For example, forever doesn’t mean forever. It means a certain period of time.
These verses don’t apply to you. Context changes the meaning. These verses only applied at that time period or to a certain group of people.
It doesn’t say it specifically, but common sense tells you it is so. An example of this would be the introduction of a distinction between public sin and private sin.
Be careful and be wary. I feel like most people should know the truth when they hear it, but the scripture does tell us hearing cometh by the word of God, so maybe some people are just not blessed to hear.