When someone fell ill, the Prophet ﷺ would touch his own saliva with his finger, then place it on the dust and say, "The dust of our land, mixed with the saliva of one of us, will heal our sick by the permission of our Lord."
حدثنا زهير بن حرب وعثمان بن أبي شيبة قالا حدثنا سفيان بن عيينة عن عبد ربه يعني ابن سعيد عن عمرة
كان النبي ﷺ يقول للإنسان إذا اشتكى يقول بريقه ثم قال به في التراب تربة أرضنا بريقة بعضنا يشفى سقيمنا بإذن ربنا
Reported by Muslim, in the chapter "The Recitation of Ruqyah for the Sick Using the Muawwidhat and Blowing," hadith no. 2194, from Zuhayr bin Harb, and Bukhari, in the chapter of Medicine, "The Ruqyah of the Prophet," hadith no. 5745, from the hadith of Sufyan bin Uyayna, with the same wording.