What is the meaning of "Say, 'I have believed in Allah and then be upright'," and what is its comprehensive explanation with some examples?

The meaning of uprightness (istiqamah) is to continuously adhere to Allah Almighty's command in a singular manner, without inclining to the right or the left. It is a comprehensive term for all commands and prohibitions. So, whoever believes in Allah and is content with Him as Lord fulfills the requirements of Lordship, achieves His pleasure, and gives thanks for His blessings. Uprightness is perseverance on the path of truth without deviation until one's appointed time comes while remaining on that path.