Fully Take Hold of the Grace of God

We're saved by grace. We live by grace. We're fueled by grace. "Grace is where we stand, live, and breathe. It is the realm of our existence. It is Christ in us and us in him." Grace empowers us to live this life. Acts 20:32 "Now I commit you to God and to the word of his grace, which can build you up and give you an inheritance among all those who are sanctified." Romans 6:14 "For sin shall no longer be your master because you are not under the law but under grace." * Why do so many teach tithing? * Please explain Romans 11:19-24.