"Every man according as he purposeth in his heart, so let him give; not grudgingly, or of necessity: for God loveth a cheerful giver." 2 Corinthians 9:7

Don't be stingy in giving beyond your tithes. Also, see 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." Luke 6:38

There have been people who missed promotions or who have run into sickness, and God has spoken to them and told them it was because of their attitude toward giving.  They tithed.  They gave.  However, their attitude was wrong.