Our generous God calls us to bring the full tithe (meaning the very first 10% of all our income) into the storehouse (our local church, where we are fed and cared for, from where we love and care for others). And He also instructs us to give offerings, above that 10%, out of gratitude for all His faithful provision to us.
Beyond commanding us to give, He tells us how He will respond to our obedience in giving... by opening the windows of Heaven and pouring blessing over us to such a degree as to overwhelm us.
What we do with what God gives us shows the world where our hearts are and helps proclaim the gospel and make disciples. We want to glorify God with every area of our lives, including our obedience in finances.