ESIC Act: Employer Obligations During Employee Sickness
The ESIC Act states:
73. Employer not to dismiss or punish employee during period of sickness, etc. — (1) No employer shall dismiss, discharge, or reduce or otherwise punish an employee during the period the employee is in receipt of sickness benefit or maternity benefit. Nor shall he, except as provided under the regulations, dismiss, discharge, or reduce or otherwise punish an employee during the period he is in receipt of disablement benefit for temporary disablement, is under medical treatment for sickness, or is absent from work as a result of illness duly certified in accordance with the regulations to arise out of pregnancy or confinement rendering the employee unfit for work.
Based on this, I think you cannot dismiss him from duties while he is on ESIC sickness leave.