Desire of Ages p.258
"The demoniac, in place of prayer, could utter only the words of Satan; yet the heart's unspoken appeal was heard. No cry from a soul in need, though it fail of utterance in words, will be unheeded."
....for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered.
Romans 8:26