Ponder

• WWizards of the Coast2021-03-19
  Official Ruling
  If you choose to shuffle your library, that includes the three cards you just looked at and put back on top of it.

Rulings via Scryfall

• WO
  Wizards of the Coast2015-02-03

  Ponder was banned in modern on February 3, 2015. Ponder, Preordain, and Rite of Flame all sped up the format considerably, either thanks to bursts of mana or increasing the consistency of combo decks. Source: https://magic.wizards.com/en/news/arcana/brief-history-modern-banned-list-2015-02-03
• WO
  Wizards of the Coast2024-03-11

  Ponder was unrestricted in vintage on March 11, 2024. Ponder has been restricted in Vintage since 2008! While not much has changed in Vintage since our last announcement, we believe that spell-based combo decks in Vintage could use a little boost. This shouldn't cause a huge shift, but it should give a few percentage points back to decks looking to find specific cards to enact their strategy more consistently. Source: https://magic.wizards.com/en/news/announcements/march-11-2024-banned-and-restricted-announcement
• WO
  Wizards of the Coast2011-09-20

  Ponder was banned in extended on September 20, 2011. To avoid repeating this, the DCI is banning the cards that have been most played in the most successful Standard and Extended decks over the past three years. For reasons similar to why these cards were banned in other formats, the DCI is banning them in Extended. Source: https://magic.wizards.com/en/news/feature/explanation-september-2011-br-changes-2011-09-20-0
• WO
  Wizards of the Coast2011-09-20

  Ponder was banned in modern on September 20, 2011. A large number of blue-red combination decks kept the field less diverse. One thing that made them so efficient was the cards that would find their combinations. Banning these should make those combination decks somewhat less efficient without removing the possibility of playing them. Source: https://magic.wizards.com/en/news/feature/explanation-september-2011-br-changes-2011-09-20-0