All the prophets had the same message, REPENT or TURN FROM EVIL. Jesus did not change this message but he provided something far more greater than a message. He provided the means to be successful at turning from evil. That is the true nugget of wisdom in the Good News.

Almost all the warnings about false teachers warn about doctrine that says your sin doesn't matter after you believe in Jesus. The devil loves deceiving people about this and getting them to believe they shall not surely die by disobeying God. Woe to them. It is very unpopular to teach the truth about God, but instead false teachers yearn to please men instead of God and those living in sin and following the ways of the "world", heap upon them preachers who teach them what their itching ears love to hear. Hosea said God's people will be destroyed for lack of knowledge. Not having true knowledge about sin and repentance has and will continue to destroy many. Galatians 1:6-9 teaches that there is only one gospel, and if any gospel message leaves out the doctrine of repentance or faith or both, you can be assured it is a false gospel.

Mark 6:12 So they went out and preached that people should repent

Acts 17:30 Truly, these times of ignorance God overlooked, but now commands all men everywhere to repent

Acts 2:38 Then Peter said unto them, Repent, and be Baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.

Ezekiel 18:30 Therefore I will judge you, O house of Israel, every one according to his ways," says the Lord GOD. "Repent, and turn from all your transgressions, so that iniquity will not be your ruin

2 Kings 17:13 Yet the LORD testified against Israel and against Judah, by all of His prophets, every seer, saying, "Turn from your evil ways, and keep My commandments.