“For he that speaketh in an unknown tongue speaketh not unto men, but unto God: for no man understandeth him; howbeit in the spirit he speaketh mysteries?’ (1 Cor.14:2 KJV)
This is referring to a language that God has made available to any believer who will receive it. It is the ability to commune with the Father empowered by the Holy Spirit. Wow!
The word “mysteries” is the Greek word “musterion”. It is defined as follows: “to initiate, learn a secret. A secret, or esoteric knowledge. It has to do with a person initiated into sacred mysteries. It has to do with information that has not been known before but which is revealed to an in-group or restricted constituency. It is defined as secrets, confided only to the initiated and not to be communicated by them to ordinary mortals. A hidden purpose or counsel. The secret counsels which govern God in dealing with the righteous, which are hidden from ungodly and wicked men but plain to the godly.
There is more. It means to initiate into the mysteries, and denotes not the mysterious (as with the Eng. word), but that which, being outside the range of unassisted natural apprehension, can be made known only by divine revelation, and is made known in a manner and at a time appointed by God, and to those only who are illumined by His Spirit.”
No wonder this wonderful language from our Lord is so fought against. As you are going throughout your day singing and praying in the Spirit, you are giving Him the permission to manifest all kinds of finished work realities in your walk. There are so many things to say but they will have to wait.
One final point. There are things in all of our hearts that we do not know how to articulate. You guessed it. The Holy Spirit will enable you to put into words before the Father all those desires, etc. He is so amazingly good and loves you and I, so much that He gave us this language to release His life to us; through us, etc.(see Proverbs 18:21) WOW!