Romans
King James Version (KJV)

“For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.”
King James Version (KJV)
10:10 For with the heart - Not the understanding only. Man believeth to righteousness - So as to obtain justification. And with the mouth confession is made - So as to obtain final salvation. Confession here implies the whole of outward, as believing does the root of all inward, religion.
Ro 10:10 For with the heart man believeth unto righteousness. Such a belief, the faith that saves, is a power over the life. It influences the actions and brings us into "the obedience of faith", in yielding to Christ, wherein is found pardon. With the mouth confession is man unto salvation. The faith of the heart must be openly confessed. This is a test of the faith. Unless Christ had provided such tests as confession and obedience we could not know whether ours was really a belief of the heart. That our faith moves us to confession is to us an assurance of salvation. The whole Christian life is a confession.