"Judge not, that ye be not judged". Matt 7:1
There is a fine line on what knowledge you choose to impart on another for good or for gossip. This line is really a matter of intent and only God can know the intent of a mans heart. If you hear that someone has a eating disorder or know it first hand you have a few choices. You could do nothing.
‘The only thing necessary for the triumph [of evil] is for good men to do nothing.’ - Edmund Burke. (yeah hes not in the bible but i've always loved this quote)
You can tell others for the sake of making this person look bad and by comparison you yourself look better.
“Do not go about spreading slander among your people. Do not do anything that endangers your neighbor’s life. I am the Lord.” Lev 19:16
Or you can impart this knowledge to someone who may be able to help and give council. Personally I believe that through prayer God will give you the discernment to know who to impart knowledge of this type that can bring someone into the situation to help begin the healing process. If you saw someone with a gun to their head most of us would not just sit and watch them shoot themselves or someone else without trying to intervene. In the same way if you knew someone was suicidal would you not try and find someone qualified to help them out. Again the act of gossip is in the intent and that is between you and God, however I know even in my own life I need to look at times I speak and really evaluate why it is I'm saying what I'm saying.
These are extreme examples but they make a point. When the situation is not life and death and you hear rumor of the "he said, she said" style....Go To The Source. Gossip is meant to alter the perception of a person or their character to the one you are sharing the gossip with. If you go to someone and say I heard this about you and would like to hear the truth from you, you stop the fire from spreading. I welcome feedback from others on this topic it is something coming up frequently for me and always consider the input of others. My personal accountability in this area will certainly be spoken of this week on here, as I ask to be called to the mat.

