Reply to Shroom2:
Unfortunately some people change the wording of that verse in their hearts or minds to say: 'if you ask God to come in your heart' instead of what it actually says: "shalt believe in thine heart". Can someone get saved by asking God to come down from heaven and enter into their heart? No, without trusting in Christ's work on the cross, a spiritual prayer won't save anyone. What is being asked that we believe from the heart? We are asked to have "faith in his blood" - Romans 3:25 That Jesus shed his blood to pay for all of your sins on the cross, that he died and rose again for your free justification.
Can we trust the feelings or state of our heart for salvation?
Jeremiah 17:9
"The heart is deceitful above all things, and desperately wicked: who can know it?"
The focus should not be on the heart but on what Christ did for us on the cross. The heart does happen to be what we believe with, not our brains, according to scripture.
But also according to scripture, we don't need to know that. God saves people when they trust Christ's atonement alone, whether they know they are believing from the heart or brain.
Will a mute person or someone who cannot talk be saved just by trusting God at his word? Absolutely. We know from Acts:
"And brought them out, and said, Sirs, what must I do to be saved? And they said, Believe on the Lord Jesus Christ, and thou shalt be saved... " - Acts 16:30-31
All a person has to do is "Believe on the Lord Jesus Christ" and they "shalt be saved." That is a promise from God and I take him at his word.