Allah's Apostle said, "May Allah's mercy be on him who is lenient in his buying, selling, and in demanding back his money."
Sahih Bukhari: Volume 3, Book 34, Number 290
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