Scenario: Rogue is hidden and sneaks up on a Wizard. Rogue attacks and hits the wizard with 1 above his AC. Can the wizard take his reaction to Shield from it?
Shield's casting time is 1 reaction, which you take when you are
hit by an attack or targeted by the Magic Missile spell.
Until the start of your next turn, you have a +5 bonus to AC, including against the triggering attack, and you take no damage from magic missile."
The wizard is arguing that the RAW is any attack that hits him. The Rogue is stating that he's hidden and that the wizard shouldn't be able to see it coming. To this the wizard argues that when you attack you lose your stealth and gives enough time to activate a reaction.