Question142: Sometimes while traveling a liquid comes out of my body, in which I am not able to recognize. What should I treat the liquid as?

Answer 142: If you performed Istibra after each urination, the liquid which comes out of your body afterward, is treated as pure.
Istibra is a recommended act for men after urinating. Its objective is to ensure that no urine is left in the urethra. There are certain ways of performing Istibra. The best way is after the passing of urine, if the anus also becomes najis, it is made clean first. Thereafter, the part between the anus and the root of penis should be pressed thrice, with the middle finger of the left hand. Then the thumb is placed on the penis, and the forefinger below it, pressing three times up to the point of circumcision, then the front part of the penis should be jerked three times

It is also considered as pure if you are doubtful whether or not it is urine, semen or other najas things.

Otherwise, if you didn’t perform Istibra or you are sure it is a kind of najas thing (such as semen or urine and etc.) it is regarded as impure.[1]

[1] . The official website of the office of Sayyid Sistani (ha).