I want to grow as an artist and I'm taking a step out, I want my music to mature.

Radio interview to Power 106, as quoted in Daily Mail, 'I'm retiring man': Justin Bieber announces that he's quitting his career as a singer during interview on national radio, 18 December, 2013

Justin Bieber announces that he's quitting his career as a singer during interview on national radio | Daily Mail Online[dailymail.co.uk]