When a Christian moves from sporadic impulse giving to giving as a way of life, he often becomes a tither. “Will a man rob God? But you have robbed me.” “How do we rob you?” “In tithes and offerings.” (Malachi 3:8)
The kindergarten Christian hears that and says, “That’s Old Testament legalism.” Jesus, too, had problems with the legalists of his day, the Pharisees. They were so careful to obey the Law – measuring even the harvest of tiny herbal seeds to give God his tenth. But they were not so devoted to the heavy concerns of God. “Woe to you Pharisees, because you give God a tenth of your mint, rue and all other kinds of garden herbs, but you neglect justice and the love of God” (Luke 11:42).
Surprisingly, Jesus did not tell them to stop tithing. What you should do, he remonstrated, is concentrate on the big ones – justice and the love of God – and don’t stop tithing. It’s better to give legalistically, apparently, than not to give illegalistically!
Tithing is the elementary, basic level of giving, but the majority of faithful church members do not reach even this stage of giving. After I had spoken on giving at a large influential church, the church business manager called me aside. The church had every sign of dynamic vitality, including a budget of over $3,000,000, a third of which was for missions – a sure sign of clear biblical priorities. “We did a demographic study of our congregation,” he said, “and discovered that if every member quit their job, went on unemployment, and began to tithe, we could double our budget!” Tithing moves the Christian from impulse, kindergarten level giving to giving as a way of life.
In a society of excess, luxury, and waste, Western Christians should cultivate a spirit of contentment and learn to say, “Enough!” (Philippians 4:10-13). We should learn to live more simply that others may simply live. At the great Lausanne Congress on Evangelism, several thousand church leaders committed themselves to this simplicity: “We cannot hope to attain this goal without sacrifice. All of us are shocked by the millions of poor and disturbed by the injustices which cause it. Those of us who live in affluent circumstances accept our duty to develop a simple lifestyle in order to contribute more generously to both relief and evangelism.” 
The incarnation and atoning sacrifice of Christ are the new model for showing generosity (1 Corinthians 8-9), not the Old Testament tithe. Christ became (materially) poor so that we through his poverty might become (spiritually) rich (1 Corinthians 8:9). Jesus, not Abraham or the Mosaic law should be our model.
What then is “excess”? Each one is accountable to one’s own master. “Who are you to pass judgment on the servant of another? (Romans 14:4 RSV). But excess must mean something. What is your excess?
 IBE (2014),476-477.