What should a person do if they find traces of prostatic fluid (madhiy) on their underwear, and they do not know when these drops were discharged, and must they check every time they suspect something of madhiy has been discharged while they are in a state of ritual purity (wudu')?

If a worshipper finds an impurity on his garment and does not know whether it was there before the prayer, after it, or during it, his prayer is valid according to the most preponderant opinion. However, it is recommended for him to repeat it as long as there is time, according to the Malikis.