HEART AND MOUTH
ROMANS 10:5-10 NKJ
5 For Moses writes about the righteousness which is of the law, “The man who does those things shall live by them.” 6 But the righteousness of faith speaks in this way, “Do not say in your heart, ‘Who will ascend into heaven?’” (that is, to bring Christ down from above) 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 which we preach): 9 that if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved. 10 For with the heart one believes unto righteousness, and with the mouth confession is made unto salvation.
This is how we start in the Christian life. Not by "being good" or going to church or making changes. All of those are great, but that's not how we start.
We start with God's word in our heart and then we confess (say) with our mouth. We believe Jesus is the Lord and that God raised Him for the dead. When we confess this with our mouth salvation, the new birth takes place in our lives.
This is the beauty and simplicity of the gospel. We don't have to talk or beg Jesus to save us. He has already done all that needs to be done. We don't have to get God to do anything special or earn His forgiveness. He has done it all through Jesus' death, burial and resurrection. We simply believe in our hearts and act on that belief by confessing our faith. Now after salvation has come, we begin to renew our minds, change our behavior and go to church. These actions are a result of salvation. They do not produce salvation.
Since God's word in our heart and in our mouth was how we started this new life, it would make sense that we continue in this principle. Believing God's word in our heart and speaking it with our mouths is a powerful way to continue our walk with God. We can apply this heart and mouth principle to who God is, what Jesus has done for us, who we are now in Christ, and what the Holy Spirit is doing in us. Don't try to reason out the "how" of this principle in your head. Heart and mouth is a spiritual truth we can apply to all areas of our lives.