Punishing Fire

• WWizards of the Coast2009-10-01
  Official Ruling
  You choose whether to pay as the triggered ability resolves.
• WWizards of the Coast2009-10-01
  Official Ruling
  If Punishing Fire has left your graveyard by the time its triggered ability resolves, you may still pay , but you won't return it to your hand. This is true even if Punishing Fire has left your graveyard and returned to it by the time its triggered ability resolves.
• WWizards of the Coast2009-10-01
  Official Ruling
  Punishing Fire's triggered ability triggers only if it's already in your graveyard at the time an opponent gains life. For example, you can cast it in response to a spell or ability that will cause an opponent to gain life. In that case, Punishing Fire will resolve first, so it will be in the graveyard by the time the opponent gains life. However, if you wait until an opponent actually gains life and then cast Punishing Fire, you won't be able to return it to your hand at that time.

Rulings via Scryfall

• WO
  Wizards of the Coast2015-02-03

  Punishing Fire was banned in modern on February 3, 2015. We have the goal of maintaining a diverse format. The heavy majority of all aggressive decks were Zoo decks. Punishing Fire was particularly punishing to anything with less than 3 toughness. Source: https://magic.wizards.com/en/news/arcana/brief-history-modern-banned-list-2015-02-03
• WO
  Wizards of the Coast2011-12-20

  Punishing Fire was banned in modern on December 20, 2011. Punishing Fire, when combined with Grove of the Burnwillows, gives a repeatable 2 damage for 3 mana. This pair of cards is commonly used, and is devastating to creature decks relying on creatures with less than 2 toughness. Tribal decks relying on 2 toughness "lords" see very little play, and this is a major barrier to their success. Source: https://magic.wizards.com/en/news/feature/explanation-december-2011-br-changes-2011-12-20