Burning books is to imprison thoughts, and forbidding words is to control speech. The former sentence is one of the works of German poet heinrich heine, and the latter sentence is of unknown origin. This sentence is not from the original work, but may have been added by later generations.

There is also a saying that these two sentences were engraved at the entrance of Dachau concentration camp in Germany. This is actually a fallacy. Arbeit is usually carved at the gate of a concentration camp in Germany.

Macht frei, that is, "labor brings freedom"