Musnad Abu Ya'la al-Mawsili 150:46

Narrated to us Muhammad ibn 'Abbad, narrated to us Sufyan, from 'Abd Rabbih ibn Sa'id, from 'Amrah, from 'Aishah: That the Messenger of Allah (peace and blessings of Allah be upon him), when there was a sore or something on a man's hand, would do this with his finger—then he said: "In the name of Allah, the soil of our land, with the saliva of some of us, our sick will be healed, by the permission of our Lord."