John Wesley on Genesis 2:16-17

Thou shall die - That is, thou shalt lose all the happiness thou hast either in possession or prospect; and thou shalt become liable to death, and all the miseries that preface and attend it. This was threatened as the immediate consequence of sin. In the day thou eatest, thou shalt die - Not only thou shalt become mortal, but spiritual death and the forerunners of temporal death shall immediately seize thee.