1 Corinthians 14:37 (KJV) If any man think himself to be a prophet, or spiritual, let him acknowledge that the things that I write unto you are the commandments of the Lord.
The church is the household of God, as we have learned from the Mass Indoctrination of the MCGI. Bro Eli Soriano explained to us that in the church there are rules that guide our conducts. These rules are the doctrines. The doctrines are the commandments of God. We are to obey the commandments.
Aside from the doctrines, there are other actions that we carry out in the church which are not commanded. Those actions are done by us voluntarily. We use our common sense and heart of love. Some of the voluntary actions we do in the church include contributions, thanksgiving, vows, doing good to our fellow men.
1 Corinthians 16:1 (KJV) Now concerning the collection for the saints, as I have given order to the churches of Galatia, even so do ye.
In the contributions, we contribute to support the work of God in the church. Like Bro Eli Soriano told us, the contributions make the church able to pay its bills and buy gadgets for the church programs. As christians, we have to help the spread of the gospel by giving our money so that the church will be able to do the work at ease.
Matthew 28:20 (KJV) Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.