待你长发及腰我一把火烧
[dài nĭ zhăng fā jí yāo wŏ yī bă huŏ shāo]
It’s a dramatic expression showing dissatisfaction and helplessness towards someone (often used in the context of unreciprocated love). It describes a situation where one's patience has run out while waiting for the other person to grow their hair long.