Jesus said to him, "I am the way, and the truth, and the life; no one comes to the Father but through Me." (John 14:6 NASB)
At this point in Jesus' ministry He knows that the cross is coming. He knows that He will soon be leaving His disciples to do that which He came to earth to do, and that is to atone for the sins of His people. It is now at this vital moment in history that His disciples need some real comforting.
They are no doubt very worried about the future. After all, on many occasions Christ had to correct their thinking that He was to establish His Kingdom right then and there. They were worried and needed a comforting word from their Master at that time more than ever.
"Do not let your heart be troubled; believe in God, believe also in Me. In My Father's house are many dwelling places; if it were not so, I would have told you; for I go to prepare a place for you. If I go and prepare a place for you, I will come again and receive you to Myself, that where I am, there you may be also. And you know the way where I am going." Thomas said to Him, "Lord, we do not know where You are going, how do we know the way?" Jesus said to him, "I am the way and the truth, and the life; no one comes to the Father but through Me." (John 14:1-6 NASB)
Jesus reassures His disciples by telling them to not be troubled. He doesn't want them to be anxious or fear in any way. He tells them because you believe in God, believe also in Me. He then explains to them how He will have a specific place prepared for each of His people and that where He is going they will go also. Now obviously He did not mean right then at that moment, or at the moment at His ascension; for it is not until the moment of death that the believer is present with the Lord in glory.
However, Christ wanted His disciples as well as every believer to know that our ultimate destiny is to be with Him throughout all of eternity. Just because He was going away then to make the atonement for sins did not in any way mean He was leaving them forever. Furthermore, He would go on to instruct them that He would not be leaving them as orphans but would send the Holy Spirit to comfort them in His absence who not only is just as good as Christ, but is God Himself just as Christ it.
The key to the whole passage and the key to Solus Christus is found in verse 6. Thomas wants to know the way, and Christ instructs Him that He Himself is the way. Christ is the only way of salvation. This is one of the key building blocks not only of the Reformation period, but of the historic Christian faith in particular in contrast to every religion in existence.
Every religion is going to tell you that Jesus is not the exclusive way to salvation. They may go as far as to say that they see Christ as "A" way or part of the way or even a good teacher, but they will not claim that Christ is the ONLY way! Jesus makes it abundantly clear in this passage that He is in fact the only way to the Father. If man wants to have a right standing before God the Father they will find it in God the Son, Jesus Christ!
We have already covered Sola Fide which is Faith alone, and this is the next step to that. If we are to have faith alone then there must be an object of our faith. There has to be something that we place that faith in. For the Christian the object of our faith is the person of Jesus Christ.
All men are sinners. The soul that sins, it will die. Every man is depraved and under the condemnation of sin. Without a remedy for sin everyone would die in their sin, choosing their sin, and spending eternity separated from their Creator. However, our faith is in Christ alone, because Jesus Christ alone is the perfect, sinless sacrifice for our sins.
Jesus Christ is the Son of God. He has always existed as God. He came to this earth to dwell among us. He added human flesh to His deity and lived a righteous life completely fulfilling the Law and thereby making Himself the only acceptable sacrifice for the sins of His people.
On the cross, the full wrath of God against sin was poured out on Jesus Christ. He paid the full penalty for sin on the cross and therefore made the atonement or payment on our behalf resulting in salvation from sin's penalty for everyone who places their faith in Christ; and in Christ alone for salvation!