1) “Amen” doesn’t just mean “may it be so.” Many people think of amen as a kind of spiritual punctuation mark – something we put at the end of prayers to mean “the prayer is over.” Those who understand the word better think of it as meaning “may it be so” and being a way of adding our agreement to what was said, but the word means much more than that and actually has a number of meanings. Amen comes from a Hebrew root which in its various forms can mean: to support, to be loyal, to be certain or sure, and even to place faith in something. At the most basic level, the word can mean simply “yes!” as we see in Paul’s statement: “For no matter how many promises God has made, they are ‘Yes’ in Christ. And so through him the ‘Amen’ is spoken by us to the glory of God” (2 Corinthians 1:20). But the central meaning of the word has to do with truth, as we will see.
2) Amen was not usually used to conclude prayers in the Bible. Although it is found many times in the Bible, its main use was to affirm praise for God (Psalm 41:13; Romans 1:25; etc.) or to confirm a blessing (Romans 15:33; etc.) – either by the speaker or the hearers. The “amen” found at the end of the Lord's Prayer in some manuscripts of the New Testament affirms the expression of praise that concludes the prayer. Perhaps because of this, over the course of the centuries it became common practice to use "amen" as the conclusion for prayers.
3) Amen is used as a characteristic of God in the Old Testament. Although the English Bible translation you use may not show it, in Isaiah 65:16 the Hebrew text speaks twice of “the God of Amen,” and this clearly uses amen as a characteristic or even a title of God. Because many translators feel this would be confusing in English, they choose to render the text as “the God of truth,” and although that is not a bad translation, it does somewhat obscure the original sense of what was written.
4) Amen is used as a characteristic of Jesus in the New Testament. Just as God is referred to as the God of Amen in the Old Testament, so in the New Testament in Revelation 3:14 “Amen" is used as a title for Jesus Christ “These are the words of the Amen, the faithful and true witness, the ruler of God's creation.” The combination of Amen with “faithful and true witness” clearly shows the connection between amen and truth.
5) Amen was used uniquely by Jesus. Jesus usually used the word amen at the beginning of his statements, and in those cases, it was sometimes translated by the Gospel writers into Greek as “truly” (Luke 4:25; 9:27; etc.). The NIV translates this in turn as “I assure you …” But a completely unique use of amen by Jesus in the New Testament is recorded by the apostle John, whose Gospel shows us that Christ frequently doubled the word at the beginning of particularly important statements. In the King James Bible this is translated “Verily, verily,” in the ESV as “truly, truly,” and in the NIV “Very truly.” The doubling of amen was not only used by Jesus, however. In the early 1960’s part of a Hebrew legal document dating from the time of Jesus was found in which an individual declares “Amen, amen, ani lo ashem” meaning “Very truly, I am innocent.” It is possible, then, that Jesus borrowed this doubled form of amen from legal language of the day. But knowing that Jesus used this expression to signify important things he wanted to stress can help us see their importance in our own study of his words. The full list of occurrences of amen being doubled in John’s Gospel is: 1:51; 3:3, 5, 11; 5:19, 24-25; 6:26, 32, 47, 53; 8:34, 51, 58; 10:1, 7; 12:24; 13:16, 20, 21, 38; 14:12; 16:20, 23; and 21:18.
It is interesting that while the New Testament writers often left untranslated certain Hebrew or Aramaic words such as abba, “father,” but immediately followed the word with a translation into Greek, they invariably left “amen” untranslated in its Hebrew form. This could possibly have been because they felt the word amen was known and understood by all their readers, but it is more likely that they knew that the word represented a range of meanings and they felt it better to simply include the word and let the reader or hearer consider the possibilities. If this is the case, we can draw a lesson from the fact. That small untranslated “amen” we read in our Bibles can mean more than just “may it be so.” We can often profitably think about what it most likely means in a given context or the intended force with which the expression was used. Finally, we should remember that “amen” certainly is not just a spiritual punctuation mark or a simple exclamation – wherever we use it we should think of it as a solemn affirmation that we are giving our personal guarantee that what was said is true!