She's always spreading/preaching the 'gospel' of good health. [=telling people about the importance of good health]
I didn't do it, and that's 'the gospel truth'. [=the absolute truth; a completely true statement]
These myths are 'accepted/taken as gospel' [=believed to be true] by many teenagers.
(..) And the shot that killed him. Was it fired from his own gun? No. No. So this investigation might move a bit quicker if you were to take my word as gospel. I've just handed you a murder inquiry. Five minutes in his flat. Four floors up. That's why they think they're safe. (..)2010 TvShow: Sherlock Title: The Blind Banker Season: 1 Episode 2