Is full covering of the turban required when wiping over it?
Chapter on Wiping over the Khuffayn (Leather Socks)
Al-Mughni
Book of Purification
Primary text
There is a narration from Ahmad that wiping over the turban suffices as wiping over the head. This implies that the likeness is in the manner of wiping, not the requirement of full coverage, meaning wiping a portion is sufficient because it is a permitted concession, similar to wiping over the khuff (leather socks).
Supporting text
Alternatively, the likeness intended is in full coverage, meaning the ruling regarding the turban follows the established dispute over the obligation to wipe over the entire head, where the stronger view is that full coverage is obligatory because wiping the turban is a substitute for the substance (wiping the head), and thus it must be equivalent in measure, unlike wiping the khuff, which is a substitute for a different act (washing), and thus not strictly limited in measure.