Fasting: Gargling When Knowing Water Will Enter the Throat
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1660
If a person knows that by gargling, water will unintentionally or forgetfully enter his throat, he must not gargle; however, if in this case he does gargle but water does not enter his throat, then based on obligatory precaution, qaḍāʾ is necessary.