20 The rest of the people will hear of this and be afraid, and never again will such an evil thing be done among you.

Read Deuteronomy 19:20 Using Other Translations

And those which remain shall hear, and fear, and shall henceforth commit no more any such evil among you.
And the rest shall hear and fear, and shall never again commit any such evil among you.
Then the rest of the people will hear about it and be afraid to do such an evil thing.