If the hair of the eyebrows, beard or moustache is so thick that the skin cannot be seen, then in such a case it is wajib to wash that hair which falls within the boundaries of the face. It is not wajib to wash the hair that is beyond the boundaries of the face. [Bahishti Zewar]. What do you mean by hair which falls within the boundaries of the face? I am stressing on the length of hair of beard. If the root of hair lies within facial limit but its other end hangs downward, say, 4 inches away from face, then please clarify whether it is wajib to wash only part of the hair which is lying within facial limit or it is wajib to wash full length of hair including its root which lies on face to the other end hanging under and away from face. Regarding washing, if the beard is thick on one particular area of face (say chin) and thin on another area of face (say jawbone). Does it mean, thin portion should be washed including skin and thick portion may exclude skin?
The wordings of the ruling which you have quoted from Bahishti Zewar they are not exactly quoted, rather the wording of the Bahishti Zewar is as follows:
Mas’ala: If the hair of beard, brow or moustache is very thick and the skin below them is not visible, then it is wajib to wash only those hair which are within the limits of the face. It is not wajib to wash the hair that are beyond the said limit. (Akhtari Bahishti Zewar, Vol. 11, p. 13)
It means that the hair of beard which fall under facial limit it is wajib to wash them and the hair which hang below exceeding the facial limit, it is not wajib to wash them. In the same way the beard of the part within the limit of face is trimmed and thin and skin is visible it is wajib to wash the skin of that part. And the part which has thick beard it is not necessary to wash that part. However, in case of thick beard it is necessary to wash the hair which are within the limit of face. It is not necessary to wash the hanging hair.
(رد المحتار للشامي 1/97 ، أركان الوضوء) (وكذا في غنية المستملى في شرح منية المصلي ص 17)
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband