From
The Didache, chapter 13.
1 But every true prophet who is willing to dwell among you is worthy of his meat,
2 likewise a true teacher is himself worthy of his meat, even as is a labourer.
3 Thou shalt, therefore, take the firstfruits of every produce of the wine-press and threshing-floor, of oxen and sheep, and shalt give it to the prophets, for they are your chief priests;
4 but if ye have not a prophet, give it unto the poor.
5 If thou makest a feast, take and give the firstfruits according to the commandment;
6 in like manner when thou openest a jar of wine or of oil, take the firstfruits and give it to the prophets;
7 take also the firstfruits of money, of clothes, and of every possession, as it shall seem good unto thee, and give it according to the commandment.