He Is Not Sure About the Discharge Whether it is Mathiyy or Otherwise
23-1-2021 | IslamWeb
Question:
AssalamualaikumI recently hit puberty and this morning I went to pray Fajr in the masjid, and after I came home and went to the toilet I saw these clear drops in my underwear.I am suspicious that it is Al mathi, but not sure. Is my prayer nullified or not?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
The clear (transparent) fluid is most likely Mathiyy (pre-seminal fluid), and it is ritually impure. Its emission necessitates washing the penis, but it does not require Ghusl of Janaabah (ritual bath for the state of major ritual impurity after sexual activity). We have stated in previous Fataawa that if a person doubts whether the discharge is Maniyy or Mathiyy, he is given the choice either to consider it Maniyy and accordingly perform Ghusl or consider it Mathiyy and, in this case, he is not required to perform Ghusl but should rather wash his penis and the parts of his body or clothes that were affected by it.
This detailing of the relevant ruling was held by the Shaafi‘i scholars, and it is the preponderant opinion adopted here in Islamweb.
Al-Mawsoo‘ah Al-Fiqhiyyah Al-Kuwaytiyyah (36/317) reads: "The Shaafi‘i scholars stated that if the discharge could be Maniyy or otherwise; i.e., it could be Wadyy (white penile secretion) or Mathiyy, he is given the choice either to perform Ghusl or ablution according to the reliable opinion in this regard. If he considers the discharge to be Maniyy, he is required to perform Ghusl, and if he considers it to be otherwise, he is only required to perform ablution and wash off its traces from his body or clothes. That is because if he implements the ruling entailed by any of these cases, he will be purified from it with certainty while, as per the basic principle, the other cases do not apply to him in the first place." [End of quote]
With regard to the prayer, if there is a probability that the discharge was emitted after the prayer, the prayer is valid because the basic principle is that it is valid as long as you had performed ablution. We have stated in previous Fataawa that if it is possible for something to take place at two different times, it should be attributed to the nearest time. As-Suyooti 
said in Al-Ashbaah wa An-Nathaa’ir (p. 59): "The basic rule is to attribute an incident to the most recent time." [End of quote]
For more benefit that incidents are attributed to the nearest time to it, please refer to Fatwa 382321.
However, if you wish to perform the prayer again so as to be on the safe side, there is nothing wrong with that. If the only possibility is that the emission of the discharge occurred before or during the prayer, then the prayer is invalid and it is obligatory on you to perform it again.
Our advice to you, dear brother, since you have recently reached puberty and become competent for religious assignments and thus accountable for your actions, is to fear Allah and beware of sins; their danger is serious indeed, as they corrupt the heart, weaken the faith, and distance the sinner from Allah, The Most Merciful. So be careful and guard your tongue, your heart, and your body against disobeying Allah, The Exalted.
For more benefit on Maniyy (prostatic fluid), please refer to Fataawa 93578, 339997, 82518, 213520, and 88058.
Allah Knows best.