A.T. Robertson Commentary 1 Corinthians 14:2

"For he that speaketh in a tongue speaketh not unto men, but unto God; for no man understandeth; but in the spirit he speaketh mysteries." — 1 Corinthians 14:2 (ASV)

For no man understandeth (ουδεις γαρ ακουε). Literally, hears, gets the sense, understands. Verb ακουω used either of hearing the sound only or getting the idea (cf. Acts 9:7; 22:9).

Mysteries (μυστηρια). Unexplained mysteries (1 Corinthians 2:7).