The believer groans together with creation, praying for full redemption and deliverance. But he is not alone in his expectation of the coming glory. The Spirit groans with him. He, who is the advance on the future glory in our hearts, also prays personally for the fulfillment of his presence through our glorification.
In Romans 8:26 we read that we do not know what to pray for as we ought, but the Spirit himself intercedes for us with groanings too deep for words.
The apostle Paul is describing an invisible reality here—a reality that could have been revealed to him in a number of different ways: either from Scripture (e.g. in the Psalms or from Jesus’ own instruction about the Spirit), or because it was revealed specifically to him as an individual, or because he knows about it from having gone up to the third heaven, where he heard things that cannot be told, which man may not utter
(2 Corinthians 12:4).
The Spirit of God is known by the Father, for he who searches hearts knows what is the mind of the Spirit, because the Spirit intercedes for the saints according to the will of God
(Romans 8:27). Believing Christians live under the protection of a perfect prayer to God. The Spirit prays it, as it were, without their consent, even though it does resound in their own hearts and it is truly in their hearts where God, who knows all things exhaustively, finds it.
Exegetes such as Ernst Käseman1 believes that the intercession here refers to speaking in tongues. However, it is a prayer in the Spirit arising from within the believer’s own heart that is spoken of here, rather than words that the believer himself speaks aloud in another language with the intention of praising God (see 1 Corinthians 14:15–17).2
26 Likewise the Spirit helps us in our weakness. For we do not know what to pray for as we ought, but the Spirit himself intercedes for us with groanings too deep for words.