Translation:

79. And pray in the small watches of the morning: (it would be) an additional prayer (or spiritual profit) for thee: soon will thy Lord raise thee to a station of Praise and Glory!

Notes (Tafseer)

2277. This is held to be addressed specially to the holy Prophet who usually prayed more than the five canonical prayers. The Tahajjud was a prayer after midnight, in the small watches of the morning.

2278. To the Prophet was to be assigned in the Hereafter the highest Post of Honour and Glory-the Maqam Mahmud, implying his excellence above all other Prophets. The immediate reference may be to the hope that the Makkan persecution will soon be over and the glorious work in Madinah will begin.