Musannaf Ibn Abi Shayba 21:372

Sufyan ibn 'Uyaynah narrated to us, from 'Abd Rabbih, from 'Amrah, from 'Aishah, that the Messenger of Allah (may Allah bless him and grant him peace) used to say to the sick person, while [mixing] his saliva with his finger: "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."