I got an impurity on my trousers. I rubbed the place a little under water. Then I used it, but the stain of impurity was still visible, as the area was wet. It touched my skin. Is the trouser impure? Is the area of my body that it touched also impure?
You rubbed the place a little under water, but if you know what type of impurity it was and what to do to remove it, then you should use that. Some sorts of impurity needs to be washed with soap or decoloring substances (like bleaching powder), but some are easy to purify by washing in water or using the flow of water.
You have to ensure yourself that the place you suppose to be impure is obvious. No place besides this is impurified. If you can ensure this then comes the point: was the way you used to purify it right?
The answer depends on what type of impurity was there. Organic and oily substances may be cleaned by using soap. If the impure substance is colour changing then you can use bleaching. Note, fruit juice (which is commonly responsible for colour changing) is not impure.
If the impure substance is caused by various human or animal body fluids (feces, semen, blood or urine), this is what you should do:
- Feces need to be washed with soap. If it is obvious, especially wash the place of impurity, though you should wash the whole clothing. It looks better.
- Blood can cause colour changes if you do not wash it immediately. But, if it stays a long time and causes a colour change then use bleach. Though, I doubt whether the long term presence of blood is impure.
- In case of urine, you should wash the whole clothing. This is because you might find it difficult to determine where exactly within the clothing the impurity is.
- In case of semen, you obviously need to wash where in the clothing it impurified. If you wash it there that is likely enough to purify it. But, it looks better to not do any sacred activities wearing such clothing. Rather, you should wash the whole of the clothing under water. If it takes too much time to get the impure place in contact with water, then it produce a spot that is hard to erase. You can use bleach to erase it.
If the clothing is of any non-white colour then bleach may cause harm to it. In that case, it is better wash the whole clothing before performing sacred activities in it. If a spot remains after washing then you should not use that to perform sacred things. (I am not sure about this point, but I tell you this as it is I think it is better)