Though the subject of tithes and offerings is not overly emphasized in the New Testament, Jesus brought up the subject of money quite often, as did the disciples. In fact, God's revealed will regarding giving can be found throughout New Testament Scriptures.
For example, 1 Corinthians 16:1 talks about a collection for the saints. In Acts 11, the disciples were asked to make contributions "for the relief of the brethren living in Judea." In Luke 12:33-34, Jesus tells his followers not to worry about money, but to concentrate on the Kingdom and they'll have what they need. "Sell your possessions and give to charity; make yourselves purses which do not wear out, an unfailing treasure in heaven, where no thief comes near, nor moth destroys. For where your treasure is, there will your heart be also."
Everyone knows it takes money to run a business or a household. Even in the face of scattered improprieties, church business is still the greatest business on earth. Churches have mortgage payments, utility bills, maintenance requirements, staff salaries and a multiplicity of miscellaneous expenditures. It's all for the blessing of God's people and the thousands of communities where churches are located. Tithes and offerings make this all happen.
There is no law in the New Testament regarding the giving of offerings, but there are no words of release either. The Old Testament has more than 400 occurrences of the word "offering" in the books of the law, and 350 in Leviticus and Numbers. Offerings consumed lots of time as well as lots of animals, birds and produce. In the morning and at twilight, day by day continually! Burnt offerings, grain offerings, drink offerings, peace offerings and more. The Old Testament people sacrificed bulls, lambs, goats, turtledoves and pigeons.
With all the offering going on, it's a wonder the Israelites ever got anything else done! But through it all, it was people's hearts that God was pursuing, and He hasn't changed. Samuel expressed God's true interest to Saul when he said, "Has the Lord as great delight in burnt offerings and sacrifices, as in obeying the voice of the Lord? Behold, to obey is better than sacrifice, and to heed than the fat of rams." (1 Samuel 15:22)
God has never been into mandatory offerings. He wants His people to have willing hearts, and to bring freewill offerings for all the various work of the church. This was the attitude of the people prior to the construction of the tabernacle.
"Then everyone came whose heart was stirred, and everyone whose spirit was willing, and they brought the Lord's offering for the work of the tabernacle of meeting, for all its service, and for the holy garments. The children of Israel brought a freewill offering to the Lord, all the men and women whose hearts were willing to bring material for all kinds of work which the Lord, by the hand of Moses, had commanded to be done." (Exodus 35:21 and 29)
The Macedonians captured this heart. "They gave offerings of whatever they could -- far more than they could afford! -- pleading for the privilege of helping out... (2 Cor. 8:3, The Message)
It's not the amount that matters, but the heart of the giver. In the temple, Jesus watched rich people putting gifts into the treasury, and saw a poor widow putting in two mites, equal to perhaps a quarter of a penny. His words speak volumes. "Truly this poor widow has put in more than all, for all these out of their abundance have put in offerings for God, but she out of her poverty put in all the livelihood that she had." (Luke 21:1-4)
Besides a fixed percentage to be given regularly as a tithe, other people, programs and pursuits in the church need periodic assistance. Sowing always equals reaping, so one can never lose when giving. Additional offerings are additional investments into the Kingdom of God.