Love From a Pure Heart
The overarching purpose of the command to stop teaching strange doctrines is love. Love is defined by God, not man. It comes out of a pure heart (right with God, given by Him), a good conscience (open and honest before God) and sincere faith (not hypocritical or a sham but fully trusting God). We see perfect love in God.
The video of the entire service including recorded Hebron congregational singing can be viewed here.