Ask HN: Do you think QA engineer should know how to code and why?

Friend of mine is a QA engineer. I been asking him to learn to code to personal and professional benefits.

Just curious do you think a QA engineer needs to know how to code? If yes, then why and which language he should learn?

As a QA they get to work on applications devloped on different tech stacks. So which language would a benefit the most for a QA engineer.