Faith in Jesus Christ as Saviour is not the same thing as faith in Jesus Christ as my Saviour, nor are these the same as believing that I am saved. The latter is assurance of salvation.
Saving faith says: “I believe in Jesus Christ for the salvation of my soul.”
Assurance of salvation says: “I believe that I have believed in Jesus Christ for the salvation of my soul.” Assurance is a particular exercise of faith, but with a different object.
We are justified by faith in Jesus Christ Rom 5:1.
We come to the knowledge of this justification also by faith, faith in Jesus’ teaching on the subject. This is shown by Rom 5:2, a less well-known text than Rom 5:1. Jesus taught that the publican was justified Lk 18:14, but neither we nor the publican would know it unless Jesus taught it. If Scripture did not teach justification by faith, one would not believe it Rom 10:17. We do not need to go up to heaven to find out Rom 10:6, because the answer is in the Scripture Rom 10:8-11.
Different objects of faith
Faith is an exercise of the soul and it must have an object which it believes. The confusion in debating faith arises from failure to discern the different objects of faith.
Faith in Jesus Christ as God’s appointed Saviour comes through hearing the Gospel Rom 10:17 and being persuaded that Jesus Christ is the Son of God Act 8:37; Jn 5:24-25 and thus He can be trusted in all that He says and does.
Faith in Jesus Christ as my Saviour comes through understanding and believing that Jesus Christ offers Himself in the Gospel to be the Saviour of all those who hear the Gospel Rev 22:17.
Some people claim to have faith in Jesus Christ and James asserts that some of them are mistaken Jam 2:17. So Paul exhorts us to examine ourselves whether we be in the faith 2Cor 13:5.
Different objects of assurance
Similarly one can be sure about different things. One may be sure about things concerning Christ, and one may be sure about things concerning oneself, and others.
Peter was sure that Jesus was the Christ, the Son of God Jn 6:69 and Jesus assured him that this conviction or assurance came from His Father in heaven Mat 16:16-17. This was not the direct testimony of the Holy Spirit to Peter’s spirit, but the teaching of Jesus informing and assuring him of something that he did not know. It is recorded in Scripture for our benefit and use to examine ourselves.
The disciples were sure that Jesus knew all things and had come from God Jn 16:30.
Some people are sure that they are saved and will go to heaven; and Jesus says that some of them are deceived. Some have this assurance through an experience and others through self-examination by the Word of God. Scripture exhorts us to make our calling and election sure 2Pe 1:10. There is a difference between making it sure to ourselves and making it sure to others. Confusion reigns by a failure to notice these distinctions.
Some people are sure that they are saved but not sure about getting to heaven; this is Arminian theology which teaches that a saved person may fall from grace. Yet such a person claims to believe Jesus Christ is his Saviour. What sort of assurance is this? Assurance of salvation, for Arminians, is not the same as assurance of getting to heaven.
Assurance about ourselves is not the same as assurance about Christ.