Command Beacon

• WWizards of the Coast2015-11-04
  Official Ruling
  If your commander isn't in the command zone (or you're not playing Commander) as the last ability resolves, nothing happens.
• WWizards of the Coast2015-11-04
  Official Ruling
  If you cast a commander from your hand, the additional cost based on the number of times you've cast it from your command zone (sometimes referred to as the "commander tax") doesn't apply. Additionally, that casting won't add to the tax if you later cast the commander from the command zone.
• WWizards of the Coast2016-11-08
  Official Ruling
  If you have two commanders with the partner ability in the command zone, Command Beacon's effect puts one of your choice into your hand, not both.
• WWizards of the Coast2020-11-10
  Official Ruling
  If you have two commanders with the partner ability in the command zone, Command Beacon's effect puts one of your choice into your hand, not both.
• WWizards of the Coast2020-11-10
  Official Ruling
  If your commander isn't in the command zone (or you don't have a commander) as the last ability resolves, nothing happens.
• WWizards of the Coast2020-11-10
  Official Ruling
  If you cast a commander from your hand, the commander tax doesn't apply. Additionally, that casting won't add to commander tax if you later cast the commander from the command zone.

Rulings via Scryfall