This question already has an answer here:
The Shiites claim that they're sad of the Imam Hussein death. And for that they make self-harm or self-flagellation (Latm اللطم) every Ashura (عاشوراء) in the purpose of showing their sadness and to punish themselves. Examples of it can be easily found over the Internet.
ولا تقتلوا أنفسكم إن الله كان بكم رحيما
And do not kill yourselves [or one another]. Indeed, Allah is to you ever Merciful.
Are there any evidence in the Quran or in the Sunnah for behavior?
Why the Shiites Marajii don't practice this behavior. It's practice only by others Shiites people?
If one Christian or another Non-Muslim decided to enter in Islam then he sees this Shiites behavior does he continue in his decision?