Sunan Abi Dawud

Sunan Abi Dawud 5034

How many times should one say "May Allah have mercy on you" to one who sneezes?
Arabic hadith text
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنِ ابْنِ عَجْلاَنَ، قَالَ حَدَّثَنِي سَعِيدُ بْنُ أَبِي سَعِيدٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَشَمِّتْ أَخَاكَ ثَلاَثًا فَمَا زَادَ فَهُوَ زُكَامٌ ‏.‏
Translation
Narrated AbuHurayrah

Respond three times to your brother when he sneezes, and if he sneezes more often, he has a cold in his head.