Amen

Amen comes from a Hebrew root meaning firm, reliable, trustworthy — the same root behind the words for faith and faithfulness. To say amen is to say truly, surely, so be it — to set one's own agreement and confidence on what has been said. When a congregation says amen to a prayer, they are making it their own; when God's promises are sealed with amen, they are declared certain.

Remarkably, Jesus turned amen into an opening word: verily, verily, I say unto you is, in the Greek, amen, amen. He prefaced his own words with the seal of certainty. And the New Testament gives amen to Christ himself as a title — in Revelation he is called the Amen, the faithful and true witness — for in him all the promises of God are yea, and in him Amen.