If you confess with your mouth…

[N]otice that in the other portion of the verses under discussion, Romans 10:9—10, Paul states that for a person to be saved, he or she must “confess” with the mouth that “Jesus is Lord.” It is important to recognize that Paul does not say “if you confess with your mouth that Jesus fulfills the Davidic promise” or “if you confess with your mouth that Jesus died for your sins.” With regard to confessing, the focus lands squarely on one specific stage of the gospel—Jesus as Lord. Why? This is not mere happenstance.

Confession of Jesus as Lord is an expression of allegiance to him as the ruling king. Paul is pointing at our need to swear allegiance to Jesus as the Lord, the ruling sovereign, precisely because this lordship stage of Jesus’s career expressly summarizes a key aspect of the gospel, describes Jesus’s current role in earthly and heavenly affairs, and is the essential reality that must be affirmed to become part of God’s family. Public acknowledgement of the acceptance of Jesus’s rule is the premier culminating act of pistis. The verb that Paul selects to describe what is necessary, homologeo, refers in this sort of context to a public declaration, as is made clear by the “with your mouth.” Paul does not envision raising your hand in church or silently praying a prayer in your heart as a sufficient “confession” (nor does Paul say that such an action couldn’t initiate salvation, but he clearly intends something more substantive). Paul is talking about something public and verbal, like what might happen at an ancient baptism.—Matthew Bates in Salvation by Allegiance Alone, 97–98 (emphasis original)