What is the ruling on using the available water on parts of the body when full purification is not possible?

Primary text

It is obligatory to use the available water on the parts of the body that can be covered when one is in the state of major ritual impurity but lacks enough water for a complete ritual bath. This obligation is established by analogy to a situation where most of the body is healthy but a part is wounded, requiring care for the healthy parts. Since the person has access to a portion of the required means (water), they are obligated to use it, similar to the obligation of covering the body during prayer or removing impurity.