Surah: 091 Ash-Shams
This is a Makki Surah, and Allaah (SWT) swears by the sun and its brightness, among other things, to say that the soul that works to purify itself will succeed and the one who allows himself to be corrupted will fail.
The people of Thamud asked their prophet to show a miracle in the form of a huge she-camel, and so it was granted to her. But it became burdensome to them when Saalih (AS) asked them to allow her to drink water from their wells on alternate days. They conspired to kill her and her offspring, despite several warnings from Saalih (AS), and so consequently they were destroyed by a punishment from Allaah (SWT).