'Truth of the Gospel' in the Bible

To them we did not yield submission even for an hour, in order that the truth of the gospel might abide unshaken among you.

But when I saw that they were not walking a straight path, in the presence of the truth of the gospel, I said to Cephas before them all. "If you, although you are a Jew, live like the Gentiles and not like the Jews, why do you try to compel the Gentiles to become Jews?

because of the hope laid up for you in heaven. Long ago you heard of this hope in the message which came to you of the truth of the gospel.