Faith is more than a thought, a mere idea in the mind. In Ephesians 4, “one faith” stands beside two related pillars of unity: “one Lord” and “one baptism.” Jesus is not only the Savior to be received; He is the Lord to be obeyed (Matthew 7:21-29; Luke 6:46-49). Jesus Himself shows the hypocrisy of calling Him “Lord” while disregarding His instructions. “Why do you call Me ‘Lord, Lord,’ and not do what I tell you?” (Luke 6:46). Jesus predicts that Judgment Day will uncover how many people make the mistake of claiming faith while remaining lawless.
Not everyone who says to Me, “Lord, Lord,” will enter the kingdom of heaven, but the one who does the will of My Father who is in heaven. On that Day many will say to Me, “Lord, Lord, did we not prophesy in Your name, and cast out demons in Your name, and do many mighty works in Your name?” And then will I declare to them, “I never knew you; depart from Me, you workers of lawlessness” (Matthew 7:21-23).
“Not everyone who says to Me ‘Lord, Lord’ will enter the kingdom of heaven.”
The early Christians well knew the meaning of “one Lord.” For example, Romans was Paul’s great letter about salvation by faith. In that letter, notice how Paul described his mission in terms of faith that obeys.
We have received grace and apostleship to bring about the obedience of faith for the sake of His name among all he nations (Romans 1:5).
[I report] what Christ has accomplished through me to bring the Gentiles to obedience—by word and deed (Romans 15:18).
[The mystery] has been made known to all nations, according to the command of the eternal God, to bring about the obedience of faith (Romans 16:26 cf. Acts 6:7).
In Acts 15, some Christians had tried to define faith in terms of the Law of Moses. Paul countered that false teaching by showing what truly counts in Christianity.
For in Christ Jesus neither circumcision nor uncircumcision counts for anything, but only faith working through love (Galatians 5:6 cf. Galatians 6:15).
What counts is faith working through love.
For neither circumcision counts for anything nor uncircumcision, but keeping the commandments of God (1 Corinthians 7:19).
In Romans, Galatians, 1 Corinthians, Ephesians and other inspired writings, Paul instructs Gentiles in faith. That one faith focuses on one Lord who does more than save us. He also commands us. He works through the one Spirit to teach us and to train us to “walk in a manner worthy of [Christ’s] calling” (Ephesians 4:1).