A Muslim should be careful regarding the purity of his heart as well as his outer body and clothing. He has to avoid impurities as much as possible. He will be excused for what is beyond his ability since Islam is the religion of ease and mercy.
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
“A number of points need to be kept in mind by every Muslim:
1) Islam is a simple and easy religion; wherever there is hardship the law is relaxed.
2) We are supposed to deal with what we see and know for sure.
3) Things are considered clean unless proven otherwise.
4) We are only required to do what is within our means and power. We will not be questioned about something we have no control over.
In light of these points, if we know that our clothes are soiled with impurity we must wash them. But if we have taken every precaution to guard against impurity, then we are excused for what is beyond our ability. So use any necessary steps that are within your power, taking into consideration the circumstances you are faced with, to avoid impurity. If in spite of your best efforts, you or your clothes become impure while you are unaware of it, do not worry about it as it falls under the category of what is forgiven.
Having said this, I must add that if you know for certain that your clothes have become impure, then you must clean them as much as possible.”