The people need to agree.
Amen: An Endorsement of Praise or Prayer
“Amen,” in both Testaments, could be employed as an affirmation of endorsement as a concluding pronouncement in connection with either praise or prayer. Note Psalm 41:13. “Blessed be Jehovah, the God of Israel, From everlasting and to everlasting. Amen, and Amen”.
Amen: The Truthfulness of the Inspired Documents
“Amen” was used on occasion at the conclusion of a letter, the design of which seems to have been to emphasize the integrity of the writing. It would be the equivalent of: “What I have written is the truth!” (see Rom. 16:27; Jude 25).
Amen: The Faithfulness of God
The term is used to stress the reliability or faithfulness of God. Listen to the prophet Isaiah. “. . . [H]e who blesses himself in the earth shall bless himself in the God of truth . . .” (65:16), or as the New English Bible renders it: “He who invokes a blessing on himself in the land shall do so by the God whose name is Amen . . .” “He is the God of truth, for in the carrying out of all His promises of blessing and threatenings of judgment, He has been successful and has shown that what He has spoken is true”.
Amen: Spoken by Christ
“Amen,” as found in the Gospel accounts, is employed by Jesus alone. In the Gospel of John, it is always used in the double format, rendered in English by “verily, verily” (25 times). It emphasizes the authority with which Christ spoke, and it takes on the essence of a “thus says the Lord”.