Hack Whatsapp Account

Hi, does anyone know how I can get to view someone's whatsapp chat history and live conversation without the person knowing it? I can login to his whatsapp account from my phone but that will require whatsapp sending the verification code his phone number and he will be notified. Is ther any way to avoid this? Alternatively is there a way to retrieve the whatsapp barcode so that I can login via web.whatsapp.com but problem is I don't have passcode to unlock his iPhone in order to do this. Appreciate if someone can help. I don't mind paying a fee . Thanks