If the iron be blunt, and one do not whet the edge, then must he apply more strength; but wisdom is profitable to give success.
1 Samuel 13:20
And all Israel went down to the Philistines, every man to get his ploughshare, and his hoe, and his axe, and his sickle sharpened,
Iron is sharpened by iron; so a man sharpeneth the countenance of his friend.
If I have sharpened my gleaming sword, And my hand take hold of judgment, I will render vengeance to mine adversaries, And will recompense them that hate me.
If one turn not, he will sharpen his sword; he hath bent his bow and made it ready,
Son of man, prophesy, and say, Thus saith Jehovah: Say, A sword, a sword is sharpened, and also furbished. It is sharpened for sore slaughter, it is furbished that it may glitter. Shall we then make mirth, saying, The sceptre of my son contemneth all wood?
Sharpen the arrows; take the shields. Jehovah hath stirred up the spirit of the kings of the Medes; for his purpose is against Babylon, to destroy it; for this is the vengeance of Jehovah, the vengeance of his temple.
And he hath given it to be furbished that it may be handled. The sword, it is sharpened, and it is furbished to give it into the hand of the slayer.
It is sharpened for sore slaughter, it is furbished that it may glitter. Shall we then make mirth, saying, The sceptre of my son contemneth all wood?
Who have sharpened their tongue like a sword, and have aimed their arrow, a bitter word;
They sharpen their tongues like a serpent; adders' poison is under their lips. Selah.