Aisha reported that whenever someone complained of an ailment, or had a sore or a wound, the Prophet ﷺ would do this with his finger. Sufyan placed his index finger on the ground and then raised it, saying, "In the name of Allah, the soil of our earth mixed with the saliva of one of us, that our sick may be healed by the permission of our Lord."
أن رسول الله ﷺ كان إذا اشتكى الإنسان الشيء منه، أو كانت به قرحة او جرح قال النبي ﷺ باصبعه هكذا- ووضع سفيان سبابته بالأرض ثم رفعها-: باسم الله، تربة أرضنا، بريقة بعضنا، ليشفى به سقيمنا بإذن ربنا.
Bukhari narrated it in the Book of Medicine (5745), and Muslim in the Book of Greetings (54:2194), via Sufyan (that is, Ibn Uyayna), who said, Abd Rabbih bin Saeed told me, from Amra, from Ayesha, and he related it.The wording given here is Muslim's. As for his saying, "the soil of our earth," the majority of scholars said that what is meant by it is the earth as a whole, so each person does this with the earth on which he lives.The meaning of the hadith, as Nawawi said, is that "he takes some of his own saliva on his index finger, then places it on the dust, so that some of it clings to the finger, and wipes it over the wounded or afflicted spot, saying these words while wiping." End of quote.