What is the ruling on performing Tayammum when dust is mixed with impermissible substances like Nura (lime/hair remover), arsenic (zarneekh), or gypsum (juss)?
Chapter on Tayammum
Al-Mughni
Book of Purification
Primary text
If the mixture affecting the dust for Tayammum involves substances that nullify its permissibility, the ruling follows the status of water mixed with pure substances. If the dust is predominant (ghalabah), then Tayammum is permissible. This is the view of Al-Qadi (The Judge).
Supporting text
Ibn Aqil holds that the mixture is forbidden, even if the contaminating substance is minimal, because it might adhere to the limb and prevent the access of dust to the skin. This restriction applies specifically to substances that adhere to the hand. For substances that do not adhere, such as barley (sha'eer), Tayammum is permissible, as stated by Ahmad, because such substances do not create a barrier between the dust and the skin.