'Weakness' in the Bible

I speak humanly on account of the weakness of your flesh. For even as ye have yielded your members in bondage to uncleanness and to lawlessness unto lawlessness, so now yield your members in bondage to righteousness unto holiness.

And in like manner the Spirit joins also its help to our weakness; for we do not know what we should pray for as is fitting, but the Spirit itself makes intercession with groanings which cannot be uttered.