Is combining wiping over a dressing and Tayammum permissible?
Chapter on Tayammum
Al-Mughni
Book of Purification
Primary text
It is not permissible to combine wiping over a dressing and Tayammum in the same location because it involves substituting two different means of purification in one place, analogous to the ruling concerning wiping over leather socks (Khuff). Furthermore, because wiping is being performed on a part that was previously purified (even if the current application was done without purity), Tayammum is not obligatory, similar to the Khuff.
Supporting text
Some scholars permit combining wiping and Tayammum based on the Hadith of Jabir concerning the man with the head wound (Shaja). This is particularly suggested when the dressing exceeds the area of necessity or when applied without prior purity, as the ruling for wiping over it is debated.