Washing off impurity
Q: If there is impurity on a table or chair, how many times do I have to wipe it? Is it necessary to wipe it three times or if no traces of impurity is seen. If traces of something invisible like urine etc are there does wiping once or twice suffice. Also if I wash blood stained or impurity stained clothes in washing machine once will they be pure? Do I have to run rinse 3 times as I feel I am wasting water.