Psalms 106:48 Blessed be the LORD, the God of Israel, from everlasting to everlasting! And let all the people say, “Amen!” Praise the LORD!
The word "Amen" (אָמֵן) properly pronounced in Hebrew "ah-mehn", means "so be it" or "may it be so", and also, "Yes, it is true!" Some scholars suggest a connection with the Hebrew word for truth, "emet" (אֶמֶת), because of the two similar root letters, "aleph"(א) and "mem" (מ). Truth ought to be confirmed. At the end of a prayer, saying "Amen" expresses the desire to affirm and confirm what was requested or proclaimed. Leha'ameen, (להאמין) means "to believe, trust or confide in", and all variations of this root (אמן) relate to "emunah" (אמונה): faith, belief, or faithfulness!
Saying "Amen" is no small matter, "...if two of you shall agree (affirm, confirm) on earth as touching anything that they shall ask, it shall be done for them of my Father which is in Heaven". When we pray in the Spirit (according to God's will) and agree together, we confirm our faith and our desire for the thing to be realized, affirmed... to be, or become true. This participation in the will of God expresses our assurance that His Word, His promises, and His love are reliable and trustworthy since He is the "way, the truth, and the life!” Experience faith by praying in the will of God together; and when you hear someone praying His will, say it confidently, "AMEN!!!"