From Tang poet Jia Dao's (
贾岛) 《
剑客》:
十年磨一剑,
霜刃未曾试。
今日把示君,
谁有不平事? — 'Ten years I've honed one sword; the frosty blade has yet to be tested. Today I hold it out to you — who has been wronged?' Often used in media headlines about long-awaited products or films.