'Truth of the Gospel' in the Bible

to whom not even for an hour did we yield in subjection, that the truth of the Gospel might continue with you.

But, when I saw that they were not walking uprightly according to the truth of the Gospel, I said to Cephas in presence of them all, "If you, being a Jew, live as do the gentiles, and not as the Jews, how do you compel the gentiles to live as do the Jews?"

because of the hope laid up for you in Heaven, of which ye heard before in the word of the truth of the Gospel,