'Fail' in the Bible

so that the Lord may fulfill His promise concerning me, saying, ‘If your sons are careful regarding their way [of life], to walk before Me in truth with all their heart and mind and with all their soul, you shall not fail to have a man (descendant) on the throne of Israel.’

Now therefore, O Lord, the God of Israel, keep for Your servant my father David that which You promised him when You said, ‘You shall not be without a man (descendant) to sit on the throne of Israel, if only your sons take heed to their way [of life] to walk before Me [according to my laws] as you have done.’

then I will establish the throne of your kingdom over Israel forever, just as I promised your father David, saying, ‘You shall not be without a man (descendant) on the throne of Israel.’

For this is what the Lord God of Israel says: ‘The bowl of flour shall not be exhausted nor shall the jar of oil be empty until the day that the Lord sends rain [again] on the face of the earth.’”

The bowl of flour was not exhausted nor did the jar of oil become empty, in accordance with the word of the Lord which He spoke through Elijah.