The couple, who both speak openly about their Christian faith, were pictured last week in tears.

When asked about the incident by paparazzi he simply showed the book.

Getting into a car, outside Baldwin's New York apartment, he said: "You got good days and bad days - it's not real if you don't have any bad days."

 

Tim Keller released book with his wife Kathy in 2011 to unpack the "the Christian understanding of marriage".

 

Bieber and Baldwin got engaged earlier this year but a date for the wedding hasn't been released.

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Pop star Justin Bieber has revealed he's been reading 'The Meaning of Marriage' as he prepares to wed girlfriend Hailey Baldwin.