Sunan Ibn Majah Book 1, Hadith 338

حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ عُمَرَ، حَدَّثَنَا عَبْدُ الْمَلِكِ بْنُ الصَّبَّاحِ، بِإِسْنَادِهِ نَحْوَهُ وَزَادَ فِيهِ ‏ "‏ وَمَنِ اكْتَحَلَ فَلْيُوتِرْ مَنْ فَعَلَ فَقَدْ أَحْسَنَ وَمَنْ لاَ فَلاَ حَرَجَ وَمَنْ لاَكَ فَلْيَبْتَلِعْ ‏"‏ ‏.‏

A similar report was narrated by 'Abdul-Malik bin As-Sabbah with a similar chain, with the additional words:"Whoever applies kohl to his eyes, let him add it an odd number of times. Whoever does that has done well, and whoever does not, there is no harm in it. And whoever dislodges (a particle of food from between the teeth) by dislodging it with his tongue, let him swallow it