“For the tithe of the people of Israel, which they present as a contribution to the Lord, I have given to the Levites for an inheritance. Therefore I have said of them that they shall have no inheritance among the people of Israel.” – Numbers 18:24
Fulltime ministers of the gospel serve us as they serve the Lord. Missionaries, pastors, and other fulltime ministry laborers, follow the Lord to administer his will. In the process, they voluntarily sacrifice a comfortable life, earning potential, and financial security. They are called to go and serve on our behalf, and we are called to pray for and support their labors through financial giving.
The Levites sacrificed leisure and wealth so God could receive greater glory and the Israelites could worship Yahweh. The tithing of every disciple was to support greater worship of the Lord. As the people supported the Levites with tithes, the Levites ordered worship for all of Israel. John Piper said that early tithing, “was used to support religious orders; it was used for religious feasting in celebration of God’s goodness; and it taught the people to fear the Lord, that is, to fear not trusting him to meet all their needs.” The disciples of God gave sacrificially to enable the fulltime ministers to increase the quality and frequency of worship.
The entire Christian church is called to support the spread of the gospel of Jesus Christ across the street and around the world. The Lord has called upon a small percentage of disciples to sacrifice their worldly benefits so they can minister fulltime in his name. Those missionaries, pastors, and ministry workers do what they do out of a love for God’s glory. But, they don’t serve the Lord without the service of others. In they same way some have been called to go, the rest have been called to give. The goers don’t go, if the givers don’t give. It is God’s divine plan to enable all of his disciples to have an important calling in the spread of the gospel to the nations. We tithe, not out of slavish obedience, but out of a joy for the spread of God’s name.
 John Piper, Sermons from John Piper (1980–1989) (Minneapolis, MN: Desiring God, 2007).