Albert Barnes on 1 Corinthians 14:4

Edifieth himself. That is, the truths which are communicated to him by the Spirit, and which he utters in an unknown language, may be valuable, and may be the means of strengthening his faith, and building him up in the hopes of the gospel, but they can be of no use to others. His own holy affections might be excited by the truths which he would deliver, and the consciousness of possessing miraculous powers might excite his gratitude. And yet, as Doddridge has well remarked, there might be danger that a man might be injured by this gift when exercised in this ostentatious manner.

(*) "tongue" "Language"