Full Sharh — Mishkat al-Masabih 1451
وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ إِذَا اشْتَكَى الْإِنْسَانُ الشَّيْءَ مِنْهُ أَوْ كَانَتْ بِهِ قَرْحَةٌ أَوْ جُرْحٌ قَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بِأُصْبُعِهِ: «بِسْمِ اللَّهِ تُرْبَةُ أَرْضِنَا بِرِيقَةِ بَعْضِنَا لِيُشْفَى سَقِيمُنَا بِإِذن رَبنَا»
English Translation
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.)
Source
Mishkat al-Masabih(مشكاة المصابيح)
Funerals
Hadith Number
1451