Would like to know regarding this following ayah. Tried searching for which surah, hadith, or dua this Ayah is in but didn't find an appropriate answer. Please help me. And would like to the meaning to it in english please.
The ayah is:
Ridham bi kadha-ihi wa tasliman li amrih.

by

I am patient for your rule O Lord, no God but you, O helper of distressed, I have no god but you, and no other idol, I am patient with your judgment. O helper of those who have no helper.
These are the words said by Imam Hussain, last moments before he was murdered.