The Conferences Of John Cassian by John Cassian
Chapter III. Of the offering of tithes and firstfruits.
For indeed by the Lord's command tithes were consecrated to the service of the Levites, but oblations and firstfruits for the priests. But this was the law of the firstfruits; viz., that the fiftieth part of fruits or animals should be given for the service of the temple and the priests: and this proportion some who were faithlessly indifferent diminished, while those who were very religious increased it, so that the one gave only the sixtieth part, and the other gave the fortieth part of their fruits. For the righteous, for whom the law is not enacted, are thus shown to be not under the law, as they try not only to fulfil but even to exceed the righteousness of the law, and their devotion is greater than the legal requirement, as it goes beyond the observance of precepts and adds to what is due of its own free will.