I Am Content With Allah as My Lord
رَضِيتُ بِاللَّهِ رَبًّا، وَبِالْإِسْلَامِ دِينًا، وَبِمُحَمَّدٍ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ نَبِيًّا
Raditu billahi rabban, wa bil-islami dinan, wa bi-Muhammadin sallallahu 'alayhi wa sallama nabiyyan.
I am content with Allah as my Lord, with Islam as my religion, and with Muhammad ﷺ as my Prophet.
What it means
This is a renewal of allegiance rather than a request. You are saying that if you were offered any other Lord, any other path and any other guide, you would still choose these. Saying it twice a day keeps faith from becoming something you merely inherited.
When and how
Say it three times in the morning and three times in the evening, and mean the word content.
Its virtue
The Prophet ﷺ said that whoever says it three times in the morning and three times in the evening, it becomes a right upon Allah to please him on the Day of Resurrection, reported in Sunan Abi Dawud 5072 and Jami at-Tirmidhi 3389.
Source
Abu Dawud 5072; At-Tirmidhi 3389hasan