There is a problem with saying that Jesus taught the Gospel as it is today. Now, at first glance, that phrase sounds like heresy. Jesus came to die for us so that we might live right? Of course. He was crucified for us.
However, the biographies of Christ are a very confusing area to go to for salvation doctrine. There are three main reasons
i) Jesus had not yet died for the most part of each biography.
ii) Jesus and John were preaching the gospel of the Kingdom to the Jews
iii) Gentiles and Jews get saved in different ways in these gospels.
Now, since the third one will probably get me attacked, I want to give some examples.
GENTILE SALVATION in the 4 Biographies of Christ
i) The Thief on the cross: He was saved simply by believing. He realised he needed a saviour, and acknowledged his sin, and asked Christ to save him. HOWEVER, He didn't even understand the blood atonement. How could he.. the disciples didn't even understand it. Noone preached it until Paul.
ii)The woman at the well, and the samaritans with her. Jesus called Samaritans "dogs" in other areas of scripture, so they were not considered jewish, even though they had jewish heritage.
Joh 4:40 So when the Samaritans were come unto him, they besought him that he would tarry with them: and he abode there two days.
Joh 4:41 And many more believed because of his own word;
Joh 4:42 And said unto the woman, Now we believe, not because of thy saying: for we have heard him ourselves, and know that this is indeed the Christ, the Saviour of the world.
These gentiles were saved by believing that Jesus is the Christ, the Saviour. They weren't baptised by John for repentance.
JEWISH SALVATION in the 4 biographies
It is important to understand what John's baptism was for.
Joh 1:31 And I knew him not: but that he should be made manifest to Israel, therefore am I come baptizing with water.
John's baptism of repentance was to MANIFEST TO ISRAEL who Jesus was. Not many of the pharisees were baptized with the baptism of repentance, and therefore, hardly any of them believed on Christ.
Look at this passage in Acts
Act 19:1 And it came to pass, that, while Apollos was at Corinth, Paul having passed through the upper coasts came to Ephesus: and finding certain disciples,
Act 19:2 He said unto them, Have ye received the Holy Ghost since ye believed? And they said unto him, We have not so much as heard whether there be any Holy Ghost.
Act 19:3 And he said unto them, Unto what then were ye baptized? And they said, Unto John's baptism.
Act 19:4 Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus.
Act 19:5 When they heard this, they were baptized in the name of the Lord Jesus.
Act 19:6 And when Paul had laid his hands upon them, the Holy Ghost came on them; and they spake with tongues, and prophesied.
These people that Paul met had partook in the baptism of John. They didn't know what the Holy Spirit was. They didn't know much about Christ, other than what John had told them. Paul comes to them, and finishes the plan of salvation that John begun for the jews. - REPENT, BE BAPTIZED, BELIEVE ON CHRIST.
The way jews were saved during this period of transition from Law to Grace varies wildly. Some of them are baptised by John, Christ is manifest to them, they believe and are baptised again in Jesus name. Other times, there is no baptism.
I did a study on this over the past few weeks, but I don't have my notes here (I am at work).
This is not the plan of salvation for today. Today's plan of salvation is found in Romans - Philemon.
Matthew - Acts is a transitional period, and even within Matthew - John, there is a transition. John is all about salvation of the gentiles, whereas Matthew is all about the Jews.
Anyone trying to get salvation doctrine out of Matthew - Acts is going to run into a tonne of problem verses. The exception is John, being that it was written much later, but it still exhibits some of the traits of the transitional period.
Some objections and answers
i) Peter preached the gospel in Acts 2.
No, he didn't. There is no blood atonement. There is no death, burial and resurrection. Peter preached from JOEL and Old Testament book about the MILLENNIAL KINGDOM being restored to Israel. The repentance and BAPTISM Peter preached was the same one John preached, that they might recieve Christ as King.
ii) The book of Acts shows the Apostles preaching the gospel.
No, it doesn't. It is an historical book about a period of time after Christ's death. It is infallible and perfect (KJB), but is not doctrinal. There are people getting saved in at least 9 different ways. Some with baptism, some without, some with tongues, some without, sometimes it mentions believing, sometimes it doesn't, although one would conclude that belief is evident in every salvation in acts.
Here are the main transitions in Acts
Law -> Kingdom (Matthew - Acts).
Jew to Gentile (Acts 8 - Jews reject Stephen. Same chapter, FIRST Gentile saved in acts. Chapter 9 - Paul, the missionary to the gentiles is saved. Chapter 10 - Cornelius is saved. By chapter 15, salvation is for the jews and gentiles, by faith alone. The problem chapter of chapter 19 is explained above).
Kingdom -> Grace ( Acts 2 - Acts 8 - Acts 28)
REPENTANCE
Now basically, you could call what I believe "Dispensationalism" but I am not a dry cleaner. Baptism is for this age, as an ordinance. Repentance, properly defined, is for this age. It is a change of mind about sin that agrees with God that man is a sinner. It is not an action. The man who repents, believes, and the man who believes repents. There is also repentance after salvation, which causes us to forsake sins.
I believe the KJB to be perfect. I believe the words used are perfect, and I believe that the perfect Bible perfectly defines itself.
Some refer to "The Law of first mention". I prefer to call it a principle. Generally, the first time the Bible uses a word, the context of that word sets up the usage for the rest of the Bible. For example, Egypt is associated with the world from the start, and it remains that way the entire Bible. Create is associated with God's goodness and it remains that way throughout the Bible.
Looking at the first three usages of the word repent
Gen 6:6 And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
Gen 6:7 And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
Exo 13:17 And it came to pass, when Pharaoh had let the people go, that God led them not through the way of the land of the Philistines, although that was near; for God said, Lest peradventure the people repent when they see war, and they return to Egypt:
The first two, God repents. God is not a sinner. He is not repenting of sin. He is repenting of GOODNESS that He initially created, because it has gone bad. The sin of mankind is grieving his heart.
When we repent, our minds are changed to agree with God on this point. We are sinners.
The first mention of man repenting is not even in reference to salvation. In fact, if one was certain inclined, it could be in reference to loss of salvation. The Jews have come OUT of Egypt (out of the world), and God "worries" that they might repent of their salvation, and go back into the world (egypt). Of course, one cannot lose their salvation, because as this passage demonstrates, God keeps us saved, and God kept them out of egypt, even though they were wicked, and some desired to go back (they said this later, when they were thirsty and hungry).
I am sorry if this makes little sense, or seems a bit scattered. I have constant headaches due to a tumor in my nasal cavity, and it makes it hard for me to collect my thoughts at times. I am going to see an ENT doctor about it very soon to get it removed.