Part of verse 87 of Surah Al-Anbiya, the prayer of Prophet Yunus from inside the whale.
It reads 'There is no god but You, glory be to You, I have surely been among the wrongdoers.' The Prophet (peace be upon him) said that no Muslim ever supplicates with these words for anything without Allah answering him (Sunan at-Tirmidhi). It is a beloved dua for distress and turning back to Allah.
- 21:87
وَذَا ٱلنُّونِ إِذ ذَّهَبَ مُغَٰضِبًۭا فَظَنَّ أَن لَّن نَّقْدِرَ عَلَيْهِ فَنَادَىٰ فِى ٱلظُّلُمَٰتِ أَن لَّآ إِلَٰهَ إِلَّآ أَنتَ سُبْحَٰنَكَ إِنِّى كُنتُ مِنَ ٱلظَّٰلِمِينَ
Wa Zan Nooni iz zahaba mughaadiban fazaanna al lan naqdira 'alaihi fanaanna al lan naqdira 'alaihi fanaadaa fiz zulumaati al laaa ilaaha illaaa Anta Subhaanaka innee kuntu minaz zaalimeen
Na Dhun-Nun alipoondoka hali ameghadhibika, na akadhani ya kwamba hatutakuwa na uwezo juu yake. Basi aliita katika giza: Hapana mungu isipo kuwa Wewe Subhanaka Uliye takasika. Hakika mimi nilikuwa miongoni mwa wenye kudhulumu.