Surah 51. Az-Zariyat, Ayah 18

See note [10] on 3:17 .

 Optional prayers before dawn are recommended, and are more likely to be accepted.

They were up early before dawn, ready for their devotions. The praying for Forgiveness and Mercy does not necessarily imply that they had committed fresh sins. Indeed they began the day with such devotions, showing their great humility before Allah and their anxious care for others, for whom they prayed as much as for themselves. See the last sentence of n. 21 to i. 5.