14:2 speaks not to men but to God . . . utters mysteries. This verse (cf. v. 14) describes the gift of tongues in a way that seems inconsistent with the gift of speaking in foreign languages mentioned in Acts 2:4–11 (although some believe that the miracle on Pentecost was a miracle of hearing). Accordingly, many argue that Paul is dealing with something different—a kind of ecstatic speech used for intimate prayer (Rom. 8:26). However, the word translated “tongue” is the normal Greek term for “language.” Secondly, Paul’s use of the term “mysteries” is to indicate a divine truth not yet disclosed; it does not have the meaning of the English word “mysterious” (2:7 note). Thirdly, vv. 10, 11, as well as v. 21, support the idea that even here Paul is speaking of human languages (12:8–10 note).
in the Spirit. That is, as opposed to speaking with his mind (vv. 13–15); even the speaker does not understand what he is saying.