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
The Prophet said, "Facilitate things to people (concerning religious matters), and do not make it hard for them and give them good tidings and do not make them run away (from Islam)."
Sahih Bukhari: Volume 1, Book 3, Number 69