'Futile' in the Bible

The LORD knows the thoughts of human beings that they are futile.

I know his gall," declares the LORD, "and it's futile; the boasting that they do is futile.

You said, "It is futile to serve God,' and, "What did we get out of it when we carried out his requirements and went about like mourners in the presence of the LORD of the Heavenly Armies?'