Ka'b b. Malik said that God's messenger used to eat with three fingers and lick his hand before wiping it. Muslim transmitted it.

وَعَنْ كَعْبِ بْنِ مَالِكٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَأْكُلُ بِثَلَاثَةِ أَصَابِعَ وَيَلْعَقُ يَدَهُ قَبْلَ أَن يمسحها. رَوَاهُ مُسلم