Mishkat al-Masabih 4224
Sa‘d said:
When I was ill the Prophet came to visit me, and putting his hand between my nipples so that I felt its coolness on my heart, he said, “You are suffering from a heart disease. Go to al-Harith b. Kalada who belongs to Thaqif, for he practices medicine, and get him to take seven of the 'ajwa dates of Medina and pound them together with their stones, then administer them to you.” 

Abu Dawud transmitted it.
وَعَن سعدٍ قَالَ: مَرِضْتُ مَرَضًا أَتَانِي النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَعُودُنِي فَوَضَعَ يَدَهُ بَيْنَ ثَدْيِيَّ حَتَّى وَجَدْتُ بَرْدَهَا عَلَى فُؤَادِي وَقَالَ: «إِنَّكَ رجلٌ مفْؤودٌ ائْتِ الْحَارِثَ بْنَ كَلَدَةَ أَخَا ثَقِيفٍ فَإِنَّهُ رجل يتطبب فليأخذ سبع تمرات منم عَجْوَةِ الْمَدِينَةِ فَلْيَجَأْهُنَّ بِنَوَاهُنَّ ثُمَّ لِيَلُدَّكَ بِهِنَّ» . رَوَاهُ أَبُو دَاوُد