How do you rewrite this sentence to begin with When he arrived it was dignity?

You can't rewrite the sentence to start with "When he arrived, it was dignity" because it doesn't make grammatical or logical sense.

"Dignity" is an abstract noun and doesn't work as a descriptor of a situation.

To rewrite the sentence, you'll need to provide the original sentence. Please share it, and I can help you rewrite it to begin with "When he arrived..."