God considers your giving to the poor as a personal gift to him, which he will be faithful to repay.
Whoever is generous to the poor lends to the LORD, and he will repay him for his deed. (Proverbs 19:17 ESV)
The poor won’t usually be able to pay us back, but God will make sure he does.
Others will water you.
Whoever brings blessing will be enriched, and one who waters will himself be watered. (Proverbs 11:25)
You will reap in the same way you give.
The point is this: Whoever sows sparingly will also reap sparingly, and whoever sows bountifully will also reap bountifully. (2 Corinthians 9:6)
God will increase your capacity for every kind of good work.
And God is able to make all grace abound to you, so that having all sufficiency in all things at all times, you may abound in every good work. As it is written, “He has distributed freely, he has given to the poor; his righteousness endures forever.” (2 Corinthians 9:8-9)
God will enrich you to be increasingly generous.
You will be enriched in every way to be generous in every way, which through us will produce thanksgiving to God. (2 Corinthians 9:11)
Not only will we increase in generosity, but our blessing others will result in them giving thanks and praise to God.