Regarding what a man should do if he sees fluid after gym exercise, the eminent Muslim scholar and renowned Da`iyah, Sheikh `Abdel Khaliq Hasan Ash-Shareef, responded as thus:
“You are required to perform wudu‘ to be eligible for Prayer. You are required to make ghusl in case the discharge ejected is maniy (semen) which is usually accompanied by desire which is not the case here. The fluid you notice is called wadi or madhi regarding which you are only required to make wudu‘ and to wash the place of your clothes or body touched by it in case it is noticed.
May Allah reward you and grant youParadise!”
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