When was it claimed for the first time that Christians could "pray in tongues" in private for self-edification?

Question

Very simple question: in the history of Christianity, when was it claimed for the first time (outside of the Bible, to avoid exegetical controversies, please) that the gift of tongues could be used in the context of private prayer, i.e. that Christians could edify themselves by speaking in tongues in their private prayers to God? What is the oldest record of a claim like that ever being made? Are there any extra-biblical writings from early Church Fathers saying this, for example?

(Notice that I'm not saying anything about "angelic languages", it could be prayers in real human languages unknown to the speaker too.)

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Evidence that this has been claimed at least once:

• How is speaking in tongues an edifying practice for individuals themselves?: https://hermeneutics.stackexchange.com/a/52555/38524

  There is perfect communication unhindered communication between the born again spirit of man and the Spirit of God. Therefore it is a perfect prayer. Such a prayer is the ultimate prayer for oneself because it is not impeded, overridden or hindered by rationalization of the will/emotion/mind of man.

  In such a prayer you are praying a perfect prayer according to God’s will. And agreeing with God means getting the highest chance of answered prayers. Answers to prayers are extremely edifying

• What are the benefits of praying in tongues?: https://www.josephprince.com/bible-questions/praying-in-spirit/benefits-tongues

  [...] Now imagine if you had a heavenly prayer language that enables you to always pray perfect prayers in harmony with God’s will, which is to bless you with good and perfect gifts (see James 1:17). This includes divine wisdom, the building up of your spirit and your faith, healing for your body, and wholeness for your mind. Praying in tongues gives you access to all these blessings. [...]

• Speaking in Tongues – Self Edification: https://www.ministrymaker.com/speaking-in-tongues-self-edification

  I, and thousands like me, have know the joy of building ourselves up in the Holy Ghost. The scriptures exhort us, “But ye, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost” (Jude 20). There is no experience any sweeter. There is nothing in our worship and praise that is anymore wonderful; there is nothing that satisfies anymore completely than the privilege of building ourselves up with the ministry of tongues.

• The mystery of self-edification by speaking in tongues: https://patrickoben.com/the-mystery-of-self-edification-by-speaking-in-tongues/

  Yes, not all believers will have the gift of speaking in tongues to serve others, but all can pray in tongues to build themselves. Pray and pray in tongues again and again and build up your spiritual life like a magnificent edifice!

• Q257 : How Can Speaking in an Unknown Tongue Edify the Speaker?: http://www.spiritandtruth.org/questions/257.htm?x=x

  [...] When taken in concert, these passages indicate that Paul recognized situations where a person with the gift of tongues might speak “privately” in a Spirit-inspired, unlearned, foreign language without the benefit of interpretation or self-understanding. Even though no public interpretation could be made, there was still spiritual purpose and benefit which accrued.

  1. Speaking mysteries (information not yet revealed by God) in the spirit “to God.”
  2. The edification of the one speaking: even in situations where he, himself, did not understand the message and remained unable to interpret its meaning (1Cor. 14:5,13).
  3. The speaker's spirit prays speaking “to himself and to God.”

• Build Yourself Up — Spirit, Soul And Body: https://emmanuelstephen.com/2016/12/13/build-yourself-up-spirit-soul-and-body/

  Beloved, if you are feeling emotionally drained or just physically tired from a hectic week, begin to pray in tongues and allow the Holy Spirit to edify you. God’s Spirit in you knows exactly what you need and will rest and recharge you — spirit, soul and body — as you yield to Him and pray in tongues. Sometimes, when I am tired after a long flight and still need to preach at a conference, I will pray in tongues to edify myself. I have found that when I do this, despite the jet lag, I will have the strength and clarity of mind to preach an anointed message and do whatever I need to do for the day.

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Related BH.SE questions:

• How is speaking in tongues an edifying practice for individuals themselves?
• Where are we to speak in tongues when no interpreter is around?
• Praying with spirit and understanding, simultaneously or sequentially?
• Are “praying in a tongue”, “praying with one's spirit” and “praying in the (Holy) Spirit” interchangeable expressions?

Answer 1

As for the practice of glossolalia being a private practice for self edification, prior to the charismatic renewal, it appears to have been a monastic practice for a long time - at least in the Eastern Orthodox tradition. Fr. Morton Kelsey wrote a book back in 1964 called, "Tongue Speaking: The History & Meaning of Charismatic Experience." In the book he writes about Greek Orthodox monastic practices:

Among some of the Orthodox clergy there is a sympathetic understanding of the practice of tongues, and I keep running across reports that it is known, and has been known through centuries in the monasteries. (p. 43)

If "jubilation" is a "de facto" unacknowledged species of glossolalia, then there are lots of references in church history to it being a form of private prayer. This would be despite the "de jure" view of many in the early church (Chrysostom, etc.) that the gift of tongues ceased to be given. Proverbs 25:2 states: "It is the glory of God to conceal a matter, and it is the glory of a king to search out a matter."

A good place to do some scholarly research is John C. Poirier's "Tongues of Angels: Concept of Angelic Languages in Classical Jewish and Christian Texts." Also, Eddie Ensely's "Sounds of Wonder, 20 Centuries of Praying in Tongues and Lively Worship."

In the early 20th century, the American Lutheran theologian, R.C.H. Lenski describes how non-conceptual sighs and groanings can sometimes be involved in intercessory prayer. In his commentary on Romans, Lenski rejects the interpretation that Romans 8:26 is a reference to literal sighs and groaning. However, in a type of admission against interest (as he was very concerned about the rise of the Pentecostal movement), he writes about that verse:

Later writers state that the charisma of tongues was a speaking in non-human language and either identify these ‘groanings’ with this non-human language or conceive of them as a parallel to it. (Interpretation of St. Paul’s Epistle to the Romans, p. 547)

Another Lutheran scholar F. E. Mayer, in his 1954 book "The Religious Bodies of America" writes the following about the gift of tongues:

In the words of St. Paul this charism is the least among several spiritual gifts, inasmuch as it does not edify the entire body and at best is a highly ecstatic form of prayer and praise for private use.

It is important to note that the word "ecstatic" was understood by the Lutherans as being more "esoteric" than a description of having an "out of control frenzy."

In the Lutheran tradition, the 19th-century theologian, George Stoeckhardt, writes about the ecstatic/esoteric nature of tongues in his "Exegetical Lectures on the First Epistle of Paul to the Corinthians." In a reference to 1 Corinthians 14:2-5 and the speaking of tongues, he writes (emphasis added):

Here the Apostle compares the gift of prophecy with speaking in tongues. In the latter gift, the Spirit moves the inner spirit of man to utter euphonious sounds with this tongue. It was an ecstatic form of speaking, which, however, was unintelligible both to the hearers as well as to the speaker himself.