Romans 14:2 - Coke's Commentary on the Holy Bible

Eateth herbs— Some of the Jews used to eat no flesh at all, and others looked upon it as a very high pitch of virtue to abstain from it in Gentile countries, and to subsist entirely on vegetables, from an apprehension, that the flesh sold in the shambles might have been offered to idols, or at least have contracted some ceremonial pollution. Possibly some of these Jewish converts might have been of the sect of the Essenes, who were peculiarly strict on this head, insomuch that they abstained not only from flesh, but from fruit. See Whitby and Doddridge.