When a Muslim says “Alhamdu-lillah” upon sneezing, it becomes incumbent on those Muslims who hear him to say “Yar-hamukallah” in response. This is the right of one Muslim on another. Instead of saying “Bless you,” “Gesundheit,” or anything else, it is better to say that which pleases Allah (subhana wa ta’ala) and is a source of Hasanaat for oneself.
This hadith also tells us to suppress our yawns and not make sounds when yawning. Whatever we do in order to obey Allah (subhana wa ta’ala) will be put as a good deed on The Scale on the Day of Judgement when our deeds will be weighed to determine our future.