Martin Luther King Jr.'s famous "I Have A Dream" speech utilizes numerous persuasive rhetorical techniques, among them parallelism and repetition. One good example of both is towards the end of the speech, beginning with "And so let freedom ring from the prodigious hilltops of New Hampshire." The section which follows sees King employing several rhetorical devices to convey his point: he uses a form of parallelism called anaphora (using the same initial set of words in several phrases consecutively), and meanwhile the use of enumeratio (listing, one by one, the various states and parts of the country in which freedom should ring) helps convey the span of what must be changed. King then uses repetition to further reinforce the appeal of this section: "and when we allow freedom to ring, when we let it ring from every village and every hamlet, from every state and every city."
The power of the final two lines of the speech relies heavily upon repetition, as well as another technique known as the "power of three," which orators often use to great effect: "Free at last, free at last, thank God Almighty, we are free at last."
Of course, King also uses parallelism and repetition throughout the section which gives the speech its name, as King repeats the refrain, "I have a dream" in between other examples of parallelism (anaphora) in which the phrase "I have a dream" precedes an example of that dream. The repetition of the refrain, in conjunction with this parallelism, serves to intensify this section to a climax.