Prayer: Praying When Drowsy, Needing to Relieve Oneself, or Wearing Tight Socks
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1144
It is disapproved for one to perform prayers when drowsy or needing to urinate or defecate. It is also disapproved for one to perform prayers while wearing tight socks that exert pressure on his feet. Apart from these instances, there are other disapproved acts mentioned in more detailed books.