There are many pro-gun/anti-gun control memes out there featuring unverifiable quotes from Adolf Hitler. This quote, though, is authentic, and even Snopes admits it (https://www.snopes.com/fact-check/to-conquer-a-nation/)
"The most foolish mistake we could possibly make would be to allow the subjugated races to possess arms. History shows that all conquerors who have allowed their subjugated races to carry arms have prepared their own downfall by so doing." -- Adolf Hitler, Hitler’s Table Talk, 1941-1944: Secret Conversations