QUESTION: Is it not true that the teaching in the gospels is for Israel and the Millennium and that the teaching for the church is found in the epistles?
RESPONSE: Was it not in the Gospels that Jesus said He would build His church? He trained and commissioned His disciples to do just that during His earthly ministry, which is related in the Gospels.
In Matthew 28, Christ tells the twelve to make disciples. Shouldn't we? In Mark 16, they are told to "preach the gospel." Don't we preach the gospel? Is it different? No! Where does our authority to preach the gospel and to make disciples come from if not from Christ's command to the twelve? They were then to teach these disciples to observe all that Christ had commanded them, which would include making disciples...on down to us today.
If Paul was the one who brought teaching to the church, and the Gospels are only for Israel, how do we deal with the fact that the church was formed before Paul came along? That wasn't Israel being formed or restored on the Day of Pentecost!
Peter and the other disciples preached the gospel before Paul was converted. It was clearly the same gospel by which Paul was converted and that he later preached.
How can one say that Paul's epistles are for the church but that Acts was a "transitional" period between Israel and the church, when Paul wrote his epistles during the period of the Book of Acts? So, we cannot ignore the Gospels and teachings of our Lord as though they apply to some past and future age but not to the church or Christians right now.