2 Corinthians 12:6 KJV
For though I would desire to glory, I shall not be a fool; for I will say the truth: but now I forbear, lest any man should think of me above that which he seeth me to be, or that he heareth of me.
Paul said that there was a time that even saying the truth might would be unwise and therefore he would forebear. To tell the truth in this case would appear to puff himself up and make him appear the fool.
There are times when forbearance is called for. Times when speaking all the truth would not give the result of glorifying the Lord.
• When the person you speak with will not receive it as truth
• When your authority in the matter or on these circumstances might be in question
• When though you know the truth you are not able to support the truth with real evidence
• When speaking the truth would tend to puff you up in the sight of others
In those cases and others it would be best to forebear though you know the truth.