How to Grow Rich by Giving

Have you ever wondered why Bill Gates has pledged 95% and Warren Buffet 99% of their wealth away to charity?
Have you also wondered why Bill Gates continues to be one of the richest men in the world after having donated over $38 billion to his charitable foundation? His wealth continues to grow at an ever-increasing pace even as he donates.
Is there a co-relation between giving money to charity and becoming richer? Can we apply the same principles to increase our net worth?