2. This can have two meanings:

(1) Pass the night standing up in the Prayer and spend only a little of it in sleep.

(2) There is no demand from you to pass the whole night in the Prayer, but have rest as well and spend a little part of the night in worship too.

But in view of the theme that follows the first meaning seems to be more relevant, and the same is supported by (Surah Ad-Dahr, Ayat 26), in which it has been said: Prostrate yourself before Him in the night and glorify Him during the long hours of night.