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. And 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. And we know that for those who love God all things work together for good, for those who are called according to his purpose. For those whom he foreknew he also predestined to be conformed to the image of his Son, in order that he might be the firstborn among many brothers. And those whom he predestined he also called, and those whom he called he also justified, and those who he justified he also glorified.
Our inarticulate longings to pray properly are an indication to us that the indwelling Spirit is already helping us by interceding for us in our hearts, making requests that the Father will certainly answer.
The Reformation Study Bible ESV in reference to Romans 8:26