He will then be truthful if it comes to the reason behind his grief...
He will then be truthful if it comes to the reason behind his grief, but his grief distracts him from taking precaution, so he mentions his name and says something which that person hates. He will in that case be backbiting him. His grief and his seeking Allāh's mercy for him are acts of righteousness, but they led him to evil without being aware of it.
Seeking Allāh's mercy for someone and feeling sad about someone are both possible without one having to mention the name of an individual then attributing to him what he dislikes. Satan stirs him to mention his name in order to void the rewards of his grief and his pleading to Allāh to have mercy on him.
Tenth: Feeling angry for the sake of Allāh Almighty: One may feel angry because of something wrong which someone did, so he shows his anger and mentions that person's wrongdoing, thus committing a wrongdoing himself without prohibiting a wrong deed. What he should have done is to show his anger specifically in that manner. This is a pitfall in which even the elite may fall. They think that feeling angry for the sake of Allāh Almighty is an excuse no matter how it is expressed, but it is not so.
If you come to know that these are the causes of backbiting, be informed that the path towards preventing the tongue from backbiting is of two types: One of them is general, whereas the other is particular: Regarding generality, one must know that he exposes himself to the wrath of Allāh Almighty when he backbites, as you have already come to know from the previous reports. And he must be informed that such wrath voids his good deeds, his acts of righteousness.
On the Day of Judgment, backbiting shifts his good deeds to the scales of those whom he had backbitten. If he has no good deeds, the backbitten person's wrongdoings will then be shifted to the backbiter's scales, and he remains the object of the wrath of Allāh Almighty and will be like one eating dead flesh. It has been narrated about the Prophet (ص) that he said, "Fire burning what is dry is not faster than backbiting as it burns the good deeds of a servant of Allāh" ( Ulūm ad-Dīn , Vol. 3, p.
140). It has been narrated that a man said to a man of virtue, "It has come to my knowledge that you speak ill of me behind my back." The virtuous man said, "Your status in my eyes does not permit me to let you fare thus with my own good deeds!" No matter how much one believes in reports coming to him, his tongue must not articulate backbiting.