Behold, those who are bent on denying the truth and on turning others away from the path of God have indeed gone far astray.
An-Nisa (The Women) Verse 167
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