'Fail' in the Bible

And if any man said unto him, Let them not fail to burn the fat presently, and then take as much as thy soul desireth; then he would answer him, Nay; but thou shalt give it me now: and if not, I will take it by force.

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 at the LORD, saying, Shall I pursue after this troop? shall I overtake them? And he answered him, Pursue: for thou shalt surely overtake them, and without fail recover all.