Why are references to the same speech worded differently?

Answer:

We use two different styles of quoting another person today. If we want to indicate that we are quoting someone word-for-word, we use quote marks. Mom said, "Tell Jim to get his lazy body out of bed right now or he's going to be late for school." But even here, we may leave out parts that are not essential to the point we want to make and we indicate that by using "...", which indicates that more was said, but we left it out. Mom said to get "... out of bed right now or he's going to be late ..." We can also refer to the message of what someone said without giving precise words. For these, we leave off the quote marks. Mom said for you to get out of bed immediately or you'll miss school.

Exact quoting is a more modern innovation. Ancient writers gave mostly what a person said, but it could be adjusted to fit the narrative more smoothly. Since the languages in biblical times did not have punctuation, you cannot assume that a quote is a word-for-word quote unless the author says it is a precise quote.

In looking at a blend of the various accounts, we realize that Jesus probably said a great deal more than what we have recorded. The various authors are giving us the highlights that they found best suited their intended audience. Hence, Matthew places more emphasis on things that his Jewish audience needed to hear. Mark wrote for the Romans in an action-packed style. Luke wrote a historical narrative for the Greeks. Because of the different audiences, different points were selected to keep the record to a reasonable length. John points this out. "And there are also many other things that Jesus did, which if they were written one by one, I suppose that even the world itself could not contain the books that would be written" (John 21:25). When you have a large quantity of material to select from, even in a single incident, each author can select a slightly different subset and still be true to the actual event.