'In the Spirit' in the Bible

Some of you were once like that; but you washed yourselves clean, you were consecrated, you were justified in the name of our Lord Jesus Christ and in the Spirit of our God.

so I tell you now, that no one is speaking in the Spirit of God when he cries, 'Cursed be Jesus,' and that no one can say, 'Jesus is Lord,' except in the holy Spirit.

For he who speaks in a 'tongue' addresses God not men; no one understands him; he is talking of divine secrets in the Spirit.

Very well then, I will pray in the Spirit, but I will also pray with my mind; I will sing praise in the Spirit, but I will also sing praise with my mind.

Otherwise, suppose you are blessing God in the Spirit, how is the outsider to say 'Amen' to your thanksgiving? The man does not understand what you are saying!