Draw cards equal to your highest
commander taxCasting a commander from the command zone costs an additional for each prior such cast that game. (CR 903.8) among your commanders. (For example, if you've
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) your one
commanderA designated card for a Commander deck, governed by the command-zone, color-identity, and Commander rules. (CR 903) from your command zone twice, draw four cards.)