Blessed be the God and Father of our Lord Jesus Christ… – Ephesians 1:3
We bless God when we say concerning the whole of His character, “Amen. This God is our God for ever and ever.” Let Him be just what the Bible says He is; we accept Him as such. Sternly just, He will not spare the guilty. Amen, blessed be His name! Infinitely gracious, ready to forgive. Amen, so let it be! Everywhere present, always omniscient. Amen, so again do we wish Him to be! Everlastingly the same, unchanging in His truth, His promise, His nature. We again say that we are glad of it, and we bless Him. He is just such a God as we love. He is indeed God to us, because He is really God, and we can see that He is so, and every attribute ascribed to Him is a fresh proof to us that Jehovah is the Lord. Thus, we bless Him by adoration.
Praise Him also in your speech. Break the silence; speak of His glory. Invite others to cry with you, “Hallelujah!” or “Hallels unto Jah!” “Praise to Jehovah!” Ascribe ye greatness unto our God. Oh, that all flesh would magnify the Lord with us!
This language is the utterance of assent to all the blessedness that is ascribed to the Lord. After hearing how great He is, how glorious He is, how happy He is, we bless Him by saying, “Amen; so let it be! So would we have it! He is none too great for us, none too blessed for us. Let Him be great, glorious and blessed, beyond all conception.” Amen. This God is our God for ever and ever. ~ C.H. Spurgeon
https://www.blueletterbible.org/comm/spurgeon_charles/sermons/2266.cfm