The quote you've mentioned, "You cannot teach a man anything; you can only help him find it within himself," is often attributed to Galileo Galilei, but it's worth noting that direct evidence of this exact phrasing from his works is lacking. It reflects a philosophical viewpoint about learning and self-discovery, often associated with Socratic teaching methods.
For a formal reference, you might cite it as:
Galilei, Galileo. (Attribution) "You cannot teach a man anything; you can only help him find it within himself." (Exact source not confirmed)
If you need a scholarly reference or more context about Galileo's ideas on education or inquiry, please let me know!