الآية رقم (4) - وَاللَّيْلِ إِذَا يَسْرِ

(4) - (And [by] the night when it passes, (4))

The night is a sign among the creation signs. This is the Quranic method of characterizing the meanings and make them as living creatures moving to fulfill specific tasks.

So, these are the oaths the are presented at the beginning of the Surah.