romans 3:4 God forbid: yea, let God be true, but every man a liar; as it is written, That thou mightest be justified in thy sayings, and mightest overcome when thou art judged. - Free Bible Online

      4. God forbid--literally, "Let it not be," that is, "Away with such a thought"--a favorite expression of our apostle, when he would not only repudiate a supposed consequence of his doctrine, but express his abhorrence of it. "The Scriptures do not authorize such a use of God's name as must have been common among the English translators of the Bible" [HODGE].
      yea, let God be--held
      true, and every man a liar--that is, even though it should follow from this that every man is a liar.
      when thou art judged--so in Ps 51:4, according to the Septuagint; but in the Hebrew and in our version, "when thou judgest." The general sentiment, however, is the same in both--that we are to vindicate the righteousness of God, at whatever expense to ourselves.

JFB.