'Fail' in the Bible

And David said to Saul, Let no man's heart fail because of him; thy servant will go and fight with this Philistine.

And David said unto Jonathan, Behold, to-morrow is the new moon, and I should not fail to sit with the king at meat: but let me go, that I may hide myself in the field unto the third day at even.

And David inquired of Jehovah, saying, If I pursue after this troop, shall I overtake them? And he answered him, Pursue; for thou shalt surely overtake them , and shalt without fail recover all .