Larger Catechism
Q 182. How doth the Spirit help us to pray?
A. We not knowing what to pray for as we ought, the Spirit helpeth our infirmities, by enabling us to understand both for whom, and what, and how prayer is to be made; and by working and quickening in our hearts (although not in all persons, nor at all times, in the same measure) those apprehensions, affections, and graces which are requisite for the right performance of that duty.1
Romans 8:26-27
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.
Psalm 10:17
O Lord, you hear the desire of the afflicted;
you will strengthen their heart; you will incline your earZechariah 12:10
“And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and pleas for mercy, so that, when they look on me, on him whom they have pierced, they shall mourn for him, as one mourns for an only child, and weep bitterly over him, as one weeps over a firstborn. (ESV)