The full ritual bath (ghusl) for a large spread-out item if ritual impurity (najasah) affects part of it

Question:
Honorable Shaykh, may Allah grant you success. This questioner says: If impurity falls on a mattress or on a large piece of the furnishings, and the impurity is on a part of it, is it obligatory to wash the whole thing?

Answer:
Wash the part that the impurity affected, if you know where it is, or wash the part that you expect the impurity to have affected and it is more likely than not.