The Spirit himself intercedes for us.
I first learned Romans 8:26 from the American Standard version: “we know not how to pray as we ought; but the Spirit himself maketh intercession for us . . .”
The New International Version—my translation of choice—has it: “We do not know what we ought to pray for, but the Spirit himself intercedes for us . . .”
The first (ASV) says we don’t know how to pray as we ought—the second (NIV) that we don’t know what we ought to pray for.
The first suggests that the Spirit intercedes when our words are inadequate—the second that he intervenes when our knowledge is deficient.
The Spirit steps in to strengthen our prayers—both the “how” and the “what”—and to intercede for us.
The Spirit is always in your prayer closet.