Bernardin de Piconio’s Commentary on Rom 8:26-27

26. Likewise also the Spirit helps our infirmity: for we know not what to pray for as we ought: but the Spirit himself prays for us with unutterable groanings.
27. But he who searches hearts, knows what the Spirit wants: because he prays for the Saints according to God.

24. We are saved by hope, not yet in effect and reality. The completion of our salvation is yet subject to hope. That which we possess is no longer a hope. The wicked pass their lives in good things, in the enjoyment of pleasure; but they groan when they come to die. The faithful groan in this life, and rejoice to leave it. I was glad in what was said tome, we will go into the house of the Lord.

26. Our weakness and infirmity are so great that we know not what to pray for, or how to pray so as to be heard. But the Spirit who dwells within us, and cares for each of us, prays for us and in us with an earnestness and intensity which no language can describe. God, who searches the heart, knows, though we know not, what the Spirit within us so earnestly longs for, and so earnestly
demands. And this prayer is always in accordance with his will, for the Spirit demands what is required for the salvation of the Saints and their advancement to glory.

Helps our infirmity. Aids us and raises us, with the strength of his Almighty hand, when we are about to sink or fail. The Spirit prays not alone, but in us, with us, for us, through us, urging and exciting us to pray.

We are so miserable, as to be in want of all things; so weak, that we cannot ask for what we want; so ignorant that we know not what to ask for. The charity of the Holy Spirit in our hearts opens our eyes to see our misery, teaches us to recognise and long for, strengthens us to ask and implore, the grace we require to make us what we ought to be, and that with fervour and earnestness which the most experienced cannot understand, much less
describe.

27. He prays for the Saints. Only for the Saints? No doubt the Holy Spirit also urges sinners to prayer, in whom as yet he does not dwell, and in such a way that their prayer is effectual, and obtains what is necessary for their salvation, if it be pious and persevering. (source)