Translation
Otherwise,
Go to footnote numberif you speak well
Go to footnote numberof (something or someone) in spirit, how will the one filling the place of one’s own self
Go to footnote numbersay Amen to your giving of thanks,
Go to footnote numbersince he does not know what you are saying?
Paraphrase
If there were no interpretation, and, in an ecstatic state you spoke words of blessing or praise, how would the one who does not know how to understand spiritual things agree to your ecstatic statement of thanks, for he cannot understand the sounds you are making?
Footnotes
1: "Otherwise"
There is a two-verse parenthetical statement between there and here. Therefore, “otherwise” means “if there is no interpretation.” Paul now continues to paint a picture of an impossible situation, given that a Spiritless tongue will never produce a Spirit-filled interpretation.
2
“to speak well of” was their way of saying “to bless or to praise” someone or something.
3
“One’s own self”: Although this word has the literal meaning of “one’s self,” or “one’s own,” it is not referring to the person speaking or writing, rather it was used of “a person who lacks education, status, intelligence, learning, or refinement.” It also meant “someone who is unskilled, an amateur, an illiterate person, a rude person.” It sounds like our English word “idiot,” and indeed we do get that English word from this Greek word.
4: “giving of thanks”:
This is where we get our word “eucharist,” which has as its first meaning “to give thanks, or show gratitude.”