The difference between a pardonable najasah (impurity) and an unpardonable one الفرق بين النجاسة المعفو عنها والنجاسة غير المعفو عنها

Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.

As to what follows:

In response to your question, we say, and with Allah Almighty lies all success:

Among the scholars are those who said that an insignificant amount of najasah (impurity) is pardonable, while among them are those who said that it is completely unpardonable [i.e. regardless of the amount]. However, there is that which is agreed upon regarding what is pardonable, and that is the remaining traces left behind after istijmar (wiping with a rock after passing stool), because istijmar does not completely remove najasah, but it is pardonable in its place.

As for everything besides this, it is an area of dispute. The majority of scholars are of the opinion that nothing of najasah is pardonable no matter how small the amount. However, there is a group of scholars who are of the opinion that whatever of it is difficult to avoid and its presence is common, then a small amount of it is pardonable. This opinion is of notable distinction, especially if we take into account that the Shari`ah has overlooked the remaining traces of najasah after istinja’ (washing with water after urination) which we have been commanded with. Thus, a small amount of najasah is pardonable if it is something difficult to avoid and its presence is common.

And Allah knows best.