There is no basis at of all of hurting oneself during the day of Ashura. This is an act of innovation. It is an imitation of Christians of hold themselves accountable for the claimed crucifixion of Jesus.
In Islam, no soul should bear the burden of another soul. Everyone is held accountable for his own actions. Nothing to that effect has been reported in any sound HadIth from the Prophet (peace be upon him) or his Companions.
None of the Imams encouraged such things, neither the four Imams, nor any others. No reliable scholars have narrated anything like this, neither from the Prophet (peace be upon him) nor from his Companions, may Allah be pleased with them, either in any authentic report or in a weak report; neither in the books of Sahih, nor in as-Sunan, nor in the Musnads. No Hadith of this nature was known during the best centuries.
Allah Almighty knows best.
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