Command Beacon

Oracle Text

T: Add C to your mana pool.

T, Sacrifice Command Beacon: Put your commander into your hand from the command zone.

Card Rulings

11/4/2015 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.
11/4/2015 If your commander isn’t in the command zone (or you’re not playing Commander) as the last ability resolves, nothing happens.
11/8/2016 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.