Zakaria bin Abi Za'idah زكريا بن أبي زائدة خالد · Medicine (Kitab Al-Tibb)

When a man complained of pain the Prophet (ﷺ) said to him pointing to his saliva and mixing it with dust :(This is) the dust of our earth, mixed with saliva of us, so that our sick is remedied with the permission of our lord.