“The first exclamation of the Divine Liturgy reveals the key to the entire celebration:
Blessed is the Kingdom of the Father and of the Son and of the Holy Spirit, now and ever and unto ages of ages.
With these words the celebrant announces the source and the goal of the divine service of the People of God, the very context and contents of the entire liturgical action. It is the Kingdom of God brought to the world by Jesus Christ, the Son of God, and mystically reigning already in the faithful disciples of Christ by the presence and power of the Holy Spirit.
The Kingdom of God is eternal life in communion with God in loving obedience to his divine will. It is life in union with the Blessed Trinity; life lived toward the Father, through the Son, in the Holy Spirit. It is the life which Christ has given to men by his incarnation, crucifixion, resurrection, and glorification. It is the life to be lived already in this world by the People of God. To bless the Kingdom of God means to love it as one’s most precious possession. The response of the people to the proclamation of blessing by the priest is with the word Amen, which means so be it. This is the solemn affirmation that indeed the blessing of God’s Kingdom is fitting and proper. It is the official confirmation that this Kingdom is indeed the ‘pearl of great price’ for the faithful, which once having found it, they will love it and serve it and desire to have it forever (Lk 13.14).” (Thomas Hopko, The Orthodox Faith: Worship, Vol. 2, pp 152-153)