In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Imaam Nawawi (rahimahulaah) said:
And amongst the people is the one who spends for his forbidden desires and enjoyment, which increases him in (nothing) except being distanced from Allaah. This person’s wealth will be means of worry for him, and Allaah’s Protection is sought!
And amongst the people is one who spends whilst seeking the Face of Allaah in that which draws him close to Allaah, and in agreement with the Sharia of Allaah. This person’s wealth will be a source of good for him.
And amongst the people is one who spends his wealth without benefit—neither in something forbidden nor in something legislated (in Islaam). This person’s wealth is a waste upon him, and indeed the Prophet (sallal-laahu-alayhi-wasallam) forbade the wasting of wealth.
Therefore, it is obligated upon a person that when he spends his wealth in that which pleases Allaah, he should have a firm belief in Allaah’s promise, as Allaah (Glorified Be He) stated in His Noble Book: وَمَآ أَنفَقۡتُم مِّن شَىۡءٍ۬ فَهُوَ يُخۡلِفُهُۖ ”And whatsoever you spend of anything (in Allah’s Cause), He will replace it.” [34:39] [end of quote] 
Narrated Abu Hurairah (radiyallaahu-anhu): Allaah’s Messenger (sallal-laahu-alayhi-wasallam) said: If one gives in charity what is equal one date-fruit from the honestly earned money—and Allaah accepts only the honestly earned money—Allaah takes it in His Right (Hand) and then enlarges its reward for that person (who has given it)– as anyone of you brings up his baby horse– so much so that it becomes as big as a mountain. 
See Sharh Riyaadus Saaliheen of Shaikh Uthaymeen (rahimahullaah) 2/201]
Bukhaari Vol 1: Hadeeth Number 1410]