Is the gift of praying in tongues for private use, or would you suggest that it could be for public use?
Firstly, I do not possess this gift. Secondly, I would be guided by what I regard as the authoritative direction of the Holy Spirit, who is the one in control of gifts. Paul says, 'I thank God that I speak in tongues more than all of you. Nevertheless, in church I would rather speak five words with my mind in order to instruct others, than ten thousand words in a tongue' (1 Corinthians 14:18–19). Also, 'But if there is no one to interpret, let each of them keep silent in church and speak to himself and to God' (1 Corinthians 14:28). So from my point of view that settles it, because in the church it's absolutely necessary that people understand what is being said, and no one is to say the Amen to anything they haven't understood (1 Corinthians 14:16).
Paul does say, 'The one who speaks in a tongue builds up himself' (1 Corinthians 14:4), so I believe that, because Paul says it. 'He edifies himself' (KJV). And if he speaks to God in a tongue, 'he utters mysteries in the Spirit' (1 Corinthians 14:2). I'm not proposing to dispute what Paul himself said. On the other hand, because I think it is Paul's point that, when it is possible to pray with the intelligence, that is, with the intellect, as well as in the Spirit, it is always preferable.
