O men! Be conscious of your Sustainer: for, verily the violent convulsion of the Last Hour will be an awesome thing!
Al-Hajj (The Pilgrimage) Verse 1
I heard Allah's Apostle saying, "The rights of a Muslim on the Muslims are to follow the funeral processions, to accept invitation and to reply the sneezer
Sahih Bukhari: Volume 2, Book 23, Number 332