Prayer: Praying with Impurity Due to Negligence in Learning
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 787
If on account of being negligent in learning the religious ruling a person does not know that prayers performed with an impure body or with impure clothing are invalid, or that, for example, semen is impure, and he performs prayers with it, the obligatory precaution is that he must perform the prayer again; and if the prescribed time has expired, he must make it up.