render unto Caesar the things which are Caesar's
A set phrase quoting Jesus's words from Matthew 22:21. Used to express the idea of giving secular authorities what is due to them, or more broadly, respecting distinct spheres of responsibility.
The phrase 'Render unto Caesar the things which are Caesar's' is a famous passage from the Bible.
When discussing the relationship between politics and religion, he quoted 'Render unto Caesar the things which are Caesar's.'