Salam to Angels
Abu Hurairah (radi Allahu anhu) narrated that Rasul Allah (sal Allahu alaihi wa sallam) said: “When Allah created Aadam and breathed the spirit into him he sneezed and said, ‘Alhamdu-lillah (Praise be to Allah).’ So he praised Allah by His leave and his Lord said to him, ‘Allah have mercy on you, O Aadam. Go to those angels – the company of them who are seated – and say As-salamu alaykum (Peace be upon you).’ So he did and the angels replied, ‘Wa alaykas salamu wa rahmatullah (and peace be on you and the mercy of Allah).’ He then returned to his Lord, and He said, ‘This is your salutation and the greeting of your offspring among them.’” [Tirmidhi]
When Aadam (alaihis salam) sneezed and thanked Allah (subhana wa ta’ala) for it, Allah said to him, ‘O Aadam! May Allah have mercy on you.’ He did not say, ‘I will be merciful to you.’ He used the former words in order to teach Aadam (alaihis salam) the words of response that a person should say when a sneezer shows gratitude to Allah and praises Him. Once Allah (subhana wa ta’ala) shows mercy to anyone then he is assured of safety, honour and favour.
This hadith teaches us to greet Muslims with ‘As-salamu alaykum,’ to return the Salam, to say ‘Alhamdu-lillah’ when we sneeze, and to say ‘Yarhamak Allah’ if a sneezer says ‘Alhamdu-lillah.’