What substances are considered impure emanating from the bodily passages?
Chapter on Praying with Impurity and Other Matters
Al-Mughni
Book of Prayer
Primary text
That which exits the two passages (spubules), such as urine, feces, maniyy (semen/pre-seminal fluid), wadi (post-urination fluid), blood, and others, are impure. There is no known difference of opinion regarding the impurity of these substances, save for a few specific matters. The impurity of human urine is established by the hadith concerning the one being punished in his grave, where the Prophet (peace be upon him) stated he did not take precautions against his urine. It is further narrated that the majority of the torment of the grave stems from urine. The ruling concerning wadi is the same as urine because it exits the passage of urine and flows along its path.
Supporting text
The fluid known as madhy (pre-ejaculatory fluid), which is thin, viscous water emerging after arousal at the tip of the penis, is judged as impure according to the apparent position of the Madhhab because it exits a passage and is not the beginning of human creation, thus resembling urine. The Prophet (peace be upon him) commanded washing the private organ from it, and the command implies obligation.