Which figure of speech is used in this text?
Now is the time to make real the promises of democracy. Now is the time to rise from the dark and desolate valley of segregation to the sunlit path of racial justice. Now is the time to lift our nation from the quicksands of racial injustice to the solid rock of brotherhood.
—Martin Luther King, Jr, "I Have a Dream" speech

 - antithesis
 - anaphora
The text uses anaphora, the repetition of the same word or words at the beginning of several phrases or clauses.
King repeats the words now is the time at the beginning of each sentence.