When unsaved people give money, time and resources to charity, they may derive pleasure from knowing they've helped others, but in a real sense, they could say, "Their gain, my loss."
When a Christian gives money, time and resources to God's purposes, we can honestly say, "Their gain, my gain."
Why? Because God tells us that when we sacrifice earthly treasure for godly purposes, we gain heavenly treasure:
Proverbs 19:17: Whoever is kind to the poor lends to the LORD, and he will reward them for what they have done.
Luke 6:38: Give, and you will receive. Your gift will return to you in
full--pressed down, shaken together to make room for more, running over,
and poured into your lap. The amount you give will determine the amount
you get back.
Hebrews 6:10: God is not unjust; he will not forget your work and the love you have shown him as you have helped his people and continue to help them.
We have a heavenly bank account with eternal rewards. How cool is that! (Matthew 6:19-20).