Quotes about tithing from throughout Christian History.
If you are a Christian, you should read Decoding Nicea. Read why here.
Irenaeus, A.D. 183 - 186
The Lord ... instead of the law enjoining the giving of tithes, [told us] to share all our possessions with the poor. (Against Heresies IV:13:3)
... oblations [i.e., offerings] in general have not been set aside. There were oblations there [among the jews], and there are oblations here [among the Christians]. There were sacrifices among the people; there are sacrifices, too, in the Church. Only the type has been changed. This is because the offering is now made, not by slaves, but by freemen.
The Lord is one and the same, but the character of a servant's offering is unique, as is that of freemen. This is so that, by the very offerings, the freedom may be indicated and displayed. With God nothing is purposeless, nor without significance, nor without design.
For this reason, they did have the tithes of their goods consecrated to him, but those who have received liberty set aside all their possessions for the Lord's purposes, giving joyfully and freely--and not only from the less valuable portions of their property, since they have the hope of better things. They are like that poor widow who cast all her living into the treasury of God. (Against Heresies IV:18:2)
Cyprian, c. A.D. 250
This seemed like it might be ambiguous enough that the staunch defender of the tithe under the New Covenant might construe it as indicating that Cyprian was also defending the tithe. He was not. He is simply saying that contributions by the church could be understood as supporting God's workers just as the tithe supported the Levitical tribe under the Old Covenant. I have not updated this language from the Ante-Nicene Fathers, lest anyone think I was updating in order to create a certain meaning.
For it is written: "No man that warreth for God entangleth himself with the affairs of this life, that he may please Him to whom he has pledged himself" [2 Tim. 2:4] As this is said of all men, how much rather ought those not to be bound by worldly anxieties and involvements, who, being busied with divine and spiritual things, are not able to withdraw from the Church, and to have leisure for earthly and secular doings! The form of which ordination and engagement the Levites formerly observed under the law, so that when the eleven tribes divided the land and shared the possessions, the Levitical tribe, which was left free for the temple and the altar, and for the divine ministries, received nothing from that portion of the division; but while others cultivated the soil, that portion only cultivated the favour of God, and received the tithes from the eleven tribes, for their food and maintenance, from the fruits which grew. All which was done by divine authority and arrangement, so that they who waited on divine services might in no respect be called away, nor be compelled to consider or to transact secular business. Which plan and rule is now maintained in respect of the clergy, that they who are promoted by clerical ordination in the Church of the Lord may be called off in no respect from the divine administration, nor be tied down by worldly anxieties and matters; but in the honour of the brethren who contribute, receiving as it were tenths of the fruits, they may not withdraw from the altars and sacrifices, but may serve day and night in heavenly and spiritual things. (Letter 65, as cited by The Ante-Nicene Fathers, vol. V)