Mishkat al-Masabih #1451

She said that when a person complained of some trouble, or if he had a sore or a wound, the Prophet would say while pointing with his finger, “In the name of God. It is the soil of our land with the spittle of one of us (the suggestion is that the Prophet took some earth on his finger and spat on it), that our sick one may be healed by our Lord’s permission.” (Bukharl and Muslim.)