'Truth of the Gospel' in the Bible

to whom we yielded no submission, not even for an hour; that the truth of the gospel might continue with you.

But when I saw that they walked not uprightly according to the truth of the gospel, I said to Peter before them all,---If thou, who art a Jew, livest sometimes after the manner of the gentiles, and not like the Jews, why dost thou now in a manner compel the gentiles to judaize?