مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 413
Purification
How to Perform Ablution - Section 2
وَعَنِ ابْنِ عَبَّاسٍ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مَسَحَ بِرَأْسِهِ وَأُذُنَيْهِ: بَاطِنَهُمَا بِالسَّبَّاحَتَيْنِ وَظَاهِرَهُمَا بإبهاميه) (رَوَاهُ النَّسَائِيّ)
Ibn ‘Abbas said that the Prophet (ﷺ) wiped his head and also the inside of his ears with his forefingers and the outside with his thumbs. Nasa’i transmitted it.
Mishkat al-Masabih, 413صَحِيحٌ (الألباني)