Furious after he was criticized by evangelicals for stumbling in his reference to a book of the Bible during the 2016 campaign, Donald J. Trump lashed out at “so-called Christians” and used an epithet in describing them to a party official, according to a new book.

Mr. Trump’s anger was aroused after he stumbled in an appearance at Liberty University by referring to Second Corinthians as “Two Corinthians” as he was competing for the votes of evangelicals — traditionally critical to a Republican’s success in the Iowa caucuses — with Senator Ted Cruz of Texas.

Allies of Mr. Cruz’s, including Bob Vander Plaats, a well-known evangelical leader in Iowa, seized on the slip-up to taunt Mr. Trump.