Every distinct wording since 2010, newest first.
July 12, 2019 · Core Set 2020
A spell or ability on the stack is an illegal target for itself.
February 1, 2010 · Worldwake
Each time a player would get priority, the game first performs all applicable state-based actions as a single event (see rule 704, "State-Based Actions"), then repeats this process until no state-based actions are performed. Then triggered abilities are put on the stack (see rule 603, "Handling Triggered Abilities"). These steps repeat in order until no further state-based actions are performed and no abilities trigger. Then the player who would have received priority does so.