The double negative phrase ”forbiddeth to abstain” as found in D&C 49:18 can be confusing and syntactically challenging for readers. While some have argued that the phrase should be read and understood literally, the Doctrine and Covenants of The Church of Jesus Christ of Latter-day Saints indicates that a literal reading is not correct. In this article I demonstrate that the phrase ”forbid to abstain” was an accepted English idiom prior to and for a few decades following the receipt of D&C 49, even though it has vanished from contemporary usage completely. The meaning of this idiomatic expression was ”command to abstain,” in opposition to its literal meaning.