John Trapp on Isaiah 48:4

Ver. 4. Becauſe I knew that thou art obſtinate] Heb. hard, obduraete: therefore do I ſo inculcate theſe things, if by any means I may mollify thee. Hypocrites are harder to be wrought upon then other ſinners.

And thy neck is an iron ſinew] Thou art utterly averſe from, yea adverſe to any good, no more bended thereunto than if the body had for every ſinew a plate of iron.

And thy brow braſſe] Sinews of iron argue a natural impotency and ſomewhat more: but brows of braſſe impudency in evil; quando pudet non eſſe impudentes, when men are ſhameleſſe in ſin, ſetting it upon the cliffe of the Rock, Ezek. 24.7. and declaring it as Sodom, Iſa. 3.9.