'Truth of the Gospel' in the Bible

To whom we gave no room - no, not for the space of a hour - as concerning to be brought into subjection: and that because that the truth of the gospel might continue with you.

But when I saw that they went not the right way after the truth of the gospel, I said unto Peter, before all men, "If thou, being a Jew, livest after the manner of the gentiles, and not as do the Jews: why causest thou the gentiles to live as do the Jews?"