Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit Himself maketh intercession for us with groanings which cannot be uttered. – Romans 8:26

(T)here is yet another sense in which the Holy Ghost advocates, and that is, He advocates our cause with Jesus Christ, with groanings that cannot be uttered. O my soul! thou art ready to burst within me. O my heart! thou art swelled with grief. The hot tide of my emotion would well-nigh overflood the channels of my veins. I long to speak, but the very desire chains my tongue. I wish to pray, but the fervency of my feeling curbs my language. There is a groaning within that cannot be uttered. Do you know who can utter that groaning? who can understand it, and who can put it into heavenly language, and utter it in a celestial tongue, so that Christ can hear it? O yes; it is God the Holy Spirit; He advocates our cause with Christ, and then Christ advocates it with His Father. He is the advocate who maketh intercession for us, with groanings that cannot be uttered.

“Let cares like a wild deluge come,
And storms of sorrow fall;
May I but safely reach my home,
My God, my heaven, my all.”

~ C.H. Spurgeon

http://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0005.cfm