In modern times we have word processing software to help us emphasize different words of phrases we want the reader to note. We can highlight, bold, italicize, underline, or print selected words in a different color. The Hebrews used to repeat a word they wanted the hearer or reader to note for emphasis.
In John 3:3, John 3:5, John 3:11 Jesus says three times in the same conversation about being born again, "Truly, truly." Not only is the word doubled, but the doubled phrase is used several times in quick succession. This means PAY ATTENTION. In John 5 in the section about the authority of the Son, Jesus again repeats "truly, truly" several times for emphasis. (John 5:19, John 5:24, John 5:25).
It is only in John we see the double wording, even in the same stories told in other chapters, where there is a single "truly."
The born-again teaching's importance is emphasized by Jesus' introduction of the doctrine by proclaiming, "Verily, verily"—or "Truly, truly," "Most assuredly," or "Amen, amen," depending on the translation. All of His "Verily, verily" statements appear in the book of John, and they are used by Christ only when He is about to teach on a profound matter. The doubled "verily" denotes that what follows is of especially weighty and solemn significance, so we are to pay special attention. (Forerunner Commentary, John Ritenbaugh)In other words, when coming across the doubled "truly" the reader should pay careful attention to the words being presented.
And it is interesting to learn about a literary device which will enhance our understanding of and love for the Word. But it goes even deeper than that. We can intensify our understanding by learning that the phrase "truly, truly" is the Hebrew word "amen."
Charles Spurgeon explains the depth of meaning behind the word amen and why it is a title for Jesus, in a sermon delivered in 1866 called The Amen. (Revelation 3:14). In the sermon, Spurgeon says that there are three ways Amen is used; when an individual or the congregation is asserting, consenting, or petitioning. He explains at one point,
He was also "the Amen" in all His teachings. We have already remarked that He constantly commenced with "Verily, verily I say unto you." Christ as teacher does not appeal to tradition, or even to reasoning, but gives Himself as His authority.Spurgeon's sermon on Amen ("truly, truly") is wonderful and I recommend reading it.
In the sermon, Spurgeon makes note of another sermon, this one delivered by Abraham Booth, called The Amen of Social Prayer. Spurgeon recommends Booth's sermon for its thorough explanation of the use of Amen. Spurgeon said,
Should you desire still further to enquire into the use and meaning of this remarkable word, there is a valuable sermon upon it in the works of Abraham Booth, which you may read, as I have done, to great advantage. If anything should lead to the revival of its use more generally in public worship, it will be a matter of great congratulation.So note we have traveled a ways away from the initial reading of the Bibles passages in John 3, whereupon one may notice a repeated use of a phrase containing a repeated word. That's the Bible, ever deeper, ever higher, ever more interesting. Jesus says truly, truly, (amen & amen), and He IS The Amen.