I agree. He continues the thought into 10.
2 For I bear them witness that they have a zeal for God, but not according to knowledge.
The Jews were having trouble letting go of following the law. That's his point in Romans, the law verses faith. In ch. 10 he's contrasting the law with the word. He's saying the word is in your heart and in your mouth.
5 For Moses writes about the righteousness that is based on the law, that the person who does the commandments shall live by them. 6 But the righteousness based on faith says, “Do not say in your heart, ‘Who will ascend into heaven?’” (that is, to bring Christ down) 7 “or ‘Who will descend into the abyss?’” (that is, to bring Christ up from the dead). 8 But what does it say? “The word is near you, in your mouth and in your heart” (that is, the word of faith that we proclaim);
He's telling them the word is what saves you, not the law of Moses.
I agree, you're either a Christian or not.
I would strongly suggest this is not what we see people in the bible did to be saved. It ignores the facts of what Jesus commanded and what the apostles taught and did to make Christians. We have about 12 examples of conversion in scripture. What do they show the people were taught and did to become Christians?
Also, Paul doesn't mention baptism in ch. 10 because he already covered the Romans being baptized into Christ in ch. 6.
6:3 Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death?
If indeed confessing with the mouth the lord Jesus and believing in your heart that God raised him from the dead is not the how of being saved, then why did God have it written down?
Why then did God make it so plain?
Why then was the emphasis of Peter's sermon both of those truths?
Being baptized in the name of Jesus Christ is first spiritual in nature.
It is to be born again of God's spirit. It is another attribute or reference to salvation
It does not involve water or any other ritual, it is a spiritual event that God does to those who repent, that is, have a change of heart.
Change of heart? From what to what? From them being lord in their lives to Jesus Christ becoming lord in their lives, from not believing in the power of God that raised him from the dead, to believing in their hearts that God did raise him from the dead.
What Jesus commanded to his disciples in the gospel period has limited application to those of us who live in this age of grace.
We must be careful to not put ourselves under the law. In the gospel period, they lived under the law even as Jesus Christ was fulfilling it.
Once Jesus Christ works were finished even to being taken up and seated at the right hand of God, then we come to the day of Pentecost when the finished product of Jesus Christ's works could be revealed.
But it was not all revealed on the day of Pentecost, it would take decades for believers to rise up and learn what God had to teach them and reveal to them.
Thus we see in Romans 6:3 Paul is writing to Christians, he is telling them about the baptism in the name of Jesus Christ and telling them about it.
When they were born again, it was a spiritual new birth. This is the wonderful news! They now could identify with Christ not only in death but in being raised from the death.
Thus Paul could write to believers that even as Christ was raised from the dead by the glory of the Father, even so we should walk in newness of life. Romans 6:4
Thus our baptism in the name of Jesus Christ is not only incredibly meaningful, but incredible in what it makes available to us!
But it all started for the unbeliever when they did two things to get saved.
1. Confessed with the mouth the lord Jesus
2. Believed in their heart that God raised him from the dead
Acts 4:33
And with great power gave the apostles witness of the resurrection of the Lord Jesus: and great grace was upon them all.
There we see again the two elements of Romans 10:9
Acts 8:5 Philip preached Christ unto them. If you were to preach Christ would you include the truths that Jesus is lord and that God raised him from the dead?
I would, and I would want to follow what the apostles did, "with great power gave the apostles witness of the resurrection of the Lord Jesus"