This applies only for males.
It doesn't invalidate your waddu if you have done Istibra (explained below) after taharat (washed with water).
Their are 5 types of penal discharges:
- wadi (liquid discharged after urination, provided it has not come in contact with urine, which can be ensured if istibra was performed)
- wazi (liquid seen after ejaculation)
- mazi (moisture discharge by a man during wooing or courtship)
1, 2 and 3 are deemed pak (clean). 4 and 5 are najs (unclean), the release of which invalidates waddu and anything that comes in contact with it is deemed najs too.
It is the liquid that, at times, comes out after urination. If it doesn't come in contact with urine it is clean.
This might be confusing. To remove that confusion we have Istibra. If one performs Istibra after urination and liquid is discharged thereafter it is deemed clean even if one doubts whether it is urine or urine came in contact with it.
What is Istibra? Shortest definition could be, "'milking' of the urethra". It ensures that no more urine is left in the urethra. How does one do that:
There are certain ways of performing Istibra, and the best of them is that after the passing of urine, if the anus also becomes najis it is made Pak first. Thereafter, the part between the anus and the root of penis should be pressed thrice, with the mid dle 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.
If one doesn't perform Istibra, and liquid is discharged it is deemed unclean. If one doubts whether he did it properly or not, it is deemed clean. And if one, doubts whether he did it or not it is deemed unclean.
Reference from Ayatullah Sayyid Ali Husaini Sistani:
Taharat » Istibra