'Fail' in the Bible

"Now therefore, Yahweh, the God of Israel, keep with your servant David my father that which you have promised him, saying, 'There shall not fail you a man in my sight to sit on the throne of Israel, if only your children take heed to their way, to walk in my law as you have walked before me.'

then I will establish the throne of your kingdom, according as I covenanted with David your father, saying, 'There shall not fail you a man to be ruler in Israel.'