I want to show some Catholic members of my family that they can’t be saved by following Catholic dogma. I plan to use Romans 10:9 and Matt. 7:21-23 as my Scriptural support. Putting these together, it seems that unless we confess and believe in the True Jesus, the one clearly defined and presented in Holy Scripture, we could find ourselves standing before Him and being told the He never knew us. The reason being that we confessed a different Jesus from the one presented in His Holy Word, a Jesus of salvation plus works. Am I understanding this correctly?
Romans 10:9 says if you confess (agree) with your mouth Jesus is Lord and believe in your heart that God raised Him from the dead you will be saved. The part of that passage we have to be very careful about is “believe in your heart” because that’s where the determining factor lies. Regardless of the official doctrinal position of whatever religious group we’re part of, it’s what we personally believe in our heart that makes the difference. According to 1 Cor. 15:1-4 we have to believe that Jesus died for our sins, that He was buried, and that He was raised on the third day to be saved. As long as we don’t “believe in our heart” that God also requires additional things of us, we’re in.
On the other side of the coin, if you research the official doctrinal position of several of our largest mainline Protestant denominations you’ll discover they don’t really believe Jesus is God in human form and they don’t really believe in a bodily resurrection. That puts their official position in conflict with Romans 10:9 because they’re requiring less than its standard. Would you conclude from this that no one from those Protestant denominations is saved? Or is it likely that some have quietly become born again on their own?
Where motives of the heart are concerned, Jesus said we’re not to judge them but to leave it to Him (Matt. 7:1-2, 1 Cor. 4:5).
And you should also remember that Matt. 7:21-23 is the conclusion of a declaration Jesus made about false prophets that began in Matt. 7:15. I’m not convinced we can apply that in a general way. Also, we have to understand what the will of the Father is. In John 6:38-40 Jesus said His father’s will is that everyone who looks to the Son and believes in Him will have everlasting life. Every true believer is doing the will of the Father where salvation is concerned.
I have not found an approach that’s based on the claim that another person’s religious views are false to be productive. They have to come to their own conclusion about that. It might work better to tell them what you believe and why and let them make the comparison. You’ll avoid polarizing them in their current position and may get some questions that could lead to a meaningful discussion.