'Vain' in the Bible

"Oh that there were one among you who would shut the doors, that you might not kindle fire on my altar in vain! I have no pleasure in you," says Yahweh of Armies, "neither will I accept an offering at your hand.

You have said, 'It is vain to serve God;' and 'What profit is it that we have followed his instructions, and that we have walked mournfully before Yahweh of Armies?