Mu'jam Kabir Tabarani 9121 — a man met a person afflicted

Tariq bin Shihab narrates that a man met a person afflicted with khanazir (scrofula, a disease of swollen glands), and he said (to the sick man): Had a pledge not been taken from me (not to reveal its cure), I would have told you. This reached Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), so he met him and said: "Tell it." He said: A pledge has been taken from me that I will not tell it to anyone. Sayyiduna Abdullah (may Allah be pleased with him) said: "He ought not to have taken that pledge from you. Make expiation for your oath and tell it." He said: Go to the urine of camels that eat arak (the toothbrush tree), cook it until it thickens, then drink it; and take the leaves of the arak, pound them and sprinkle them over it. (The narrator) said: He did so and was cured.