'Truth of the Gospel' in the Bible

to whom not even for an hour did we yield in subjection, in order that the truth of the gospel might remain continually with you.

But when I saw that they were not being straightforward with the truth of the gospel, I said to Cephas in the presence of [them] all, "If you, [although you] are a Jew, live like a Gentile and not like a Jew, how can you try to compel the Gentiles to live like Jews?"