Imam Sadiq (a.s) quoted on the authority of God's Prophet (a.s): “
I saw something strange. I saw a man who was walking behind an animal. The animal slipped and fell down. The man said: “I wish you die!” The guardian angel on the right side said: “This was not a good deed to be recorded by me.” The guardian angel on the left side said: “This was not a sin to be recorded by me.” Then there came revelation to the guardian angel on the left side: “You must record whatever deeds that the guardian angel on the right side does not record.”