In the New Testament, we find no mention of “collecting firstfruits” from believers. “Firstfruits” is a picture of Christ or His church (I Corinthians 15:20,23 and II Thessalonians 2:13).

In Old Testament times, the Israelites were instructed to "bring the best of the firstfruits of your soil to the house of the LORD your God."  (Exodus 34:26)  There were several occasions on which this was to be done, including at Passover (Leviticus 23:10-14) and at Pentecost. (Leviticus 23:15-17)  

Bringing the firstfruits was an act of worshipping God, acknowledging Him as their Provider, the Creator of all they had. It was an act of trust, thanksgiving, and obedience. The offerings were actually placed on an altar, and parts were given to the Levites to live from, since the Levites had no inheritance in the land. (Deuteronomy 18:12)

Someone might wonder if this would mean Christians today should support their church leaders.  It is not wrong for a congregation to sometimes contribute to a church servant's needs.  For instance, the Apostle Paul writes in I Corinthians 9:11, "If we have sown spiritual seed among you, is it too much if we reap a material harvest from you?" This was especially true of those traveling evangelists of the early church.  The congregations did not build houses for them to live in, but they often provided "food and drink."  (I Corinthians 9:4)  

However, in verse 12 Paul states, "But we did not use this right…” (In other words, Paul never used this right or privilege to ask for support.) In verse 18 he writes, "What then is my reward?  Just this:  that in preaching the gospel I may offer it free of charge." 

It wasn't only from the Corinthian church that Paul declined support.  He writes in II Thessalonians 3:7,8, "…We were not idle when we were with you, nor did we eat anyone's food without paying for it…  We worked night and day… so that we would not be a burden to any of you."

Christians are not under the Law. All the regulations of the Law ended when “he (Jesus) took it away, nailing it to the cross,” Colossians 2:13, 14. However, Christians have given their “all” to God to do His will. We are to be good stewards of our time, our talents, and our money.