2 “‘I know your works, your toil and your patient endurance, and how you cannot bear with those who are evil, but have tested those who call themselves apostles and are not, and found them to be false. 3 I know you are enduring patiently and bearing up for my name’s sake, and you have not grown weary. 4 But I have this against you, that you have abandoned the love you had at first.
Just because a Christian is sound in doctrine doesn’t make him complete before God. The Ephesian church started pedaling backwards with the love they once showed in Christ by becoming more insensitive to others, probably treating them more harshly, being void of love. Not only should we obtain sound doctrine but it has to be accompanied with love. In the Book of Ephesians, we see how they used to be before Jesus sent them this letter (warning) written by the hand of the Apostle John. In Ephesians 1:15-16 it says, 15 For this reason, because I have heard of your faith in the Lord Jesus and your love toward all the saints, 16 I do not cease to give thanks for you, remembering you in my prayers, 17 that the God of our Lord Jesus Christ, the Father of glory, may give you the Spirit of wisdom and of revelation in the knowledge of him.
If your brother or sister in Christ has a different understanding that does not concern core doctrine of scripture, we should not label them as heretics or false. If a Christian disagrees on any fundamentals of doctrine, either they don’t know the Bible very well or they are deceived and without their knowledge are deceiving others. In a case like that, we must show them love with correction, pointing them to the truth because most likely they haven’t come to a true saving faith in Jesus Christ. Regardless of the circumstance, we have to love them but without compromising with the truth.