People are quick to say, and rightly so, that we cannot judge the heart. That statement may need some qualification.
It’s interesting that our courts are able to establish motive in crimes, but we cannot in religion, some say. Certainly, we do not condemn people, for that is not our job (so Matthew 7:1), but we must judge teachings, works, and doctrines (so John 7:24; 1 John 4:1).
Jesus said that one’s words and actions spring from the heart, hence, in a real sense, when we do the necessary and righteous judging, we are touching on heart issues. For example, when someone lies, does that not say something about the heart?
Of course, only God knows the heart completely. The verdict of eternal destiny lies with him. That doesn’t mean, however, that we cannot be good judges of what lies within our purview.