Surah 15. Al-Hijr, Ayah 99

Lit., "till there comes unto thee that which is certain (al-yaqin)" - a term which in the Qur'an is often used as a metonym for "death" (Bukhari, Kitab-at-Tafsir). However, see also the earliest occurrence of this term in 74:47 .

 i.e., lit., what is certain—death.

Yaqin: Certainty; the Hour that is Certain; death.