Can anyone be saved without speaking (confessing) with their mouth?
"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): 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. For with the heart one believes unto righteousness, and with the mouth confession is made unto salvation" (Romans 10:8-10).
"There is ... one faith" (Ephesians 4:4, 5). Meaning that there is only one system of belief for Christians.
"Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it. Because narrow is the gate and difficult is the way which leads to life, and there are few who find it" (Matthew 7:13-14).
"But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed" (Galatians 1:8).