Surah 54. Al-Qamar, Ayah 26

I.e., soon. In classical Arabic, the term ghadan ("tomorrow") often applies to a relatively near future, signifying "tomorrow" (in its literal sense) as well as "in time" or "soon". Hence - as pointed out by all authorities - it may have been used in the above context with reference to the Last Hour, which in the first verse of this very surah is spoken of as having "drawn near".