It’s often said, “I couldn’t have done it without you.” I'd like to add, “Thank you so much for helping so generously.”
The apostle Paul wrote to his friend Philemon, saying that he was returning the runaway slave Onesimus. (Onesimus’ name meant “useful.”) Mr. Useful had actually made himself indispensable to the Christian community, and his living testimony of usefulness and willingness to serve inspired Paul to implore Philemon to treat the returning runaway slave not as a criminal, but as a brother in Christ—an equal.
In our society, we might apply the principle to professional ministers and the “lay” Christians who volunteer considerable amounts of time, expertise, and financial resources. The professional clergy and their paid staff, organized ministries, or churches could not function without a community of true believers—believers in the cause of the gospel of Christ.
And what is the gospel? It's the good news that God is a personal God, who passionately desires to have an intimate experience with you now and forever.
Jesus said in the Sermon on the Mount that doing the acts of righteousness and giving alms to the needy are godly acts (Matthew 6:1), but to keep them quiet. Because God acts with justice, mercy, compassion, forgiveness, and love, and because we want to be like Him in all things, we are moved to go where we are needed, to liberate those in bondage, to bring Jesus’ healing balm to His children. When we do the acts of righteousness unselfishly and without expecting reward or payment, we not only strengthen those we serve, but ourselves as well, knowing that we have been instruments in the hands of God.
Run or walk to raise funds for a charity. Sign up to teach, carry equipment, lay block, or raise a roof. Sponsor a needy child or orphan in a 
foreign country (the picture is of one of my sponsored children). Pray for your local church, denomination, and your favorite ministries regularly. Volunteer to work one afternoon a month at the food bank. Advocate in a CASA program at your local court system. Donate blood. Tutor at an after-school program. Develop relationships with children in a poor neighborhood and mentor them on the weekends with outings, as some of my friends do.
God doesn’t need our money or our muscle to “finish His work.” He can just speak the word and it's perfectly created. But we need to exercise both action and finances to build faith and trust in His providence. Volunteering is ultimately for our own good! Simple acts of usefulness really can change the world.
