Historical Rules · 1 October 2009
Rule 901.4
Official source text from the 1 October 2009 Rules release
At the start of the game, each player shuffles his or her planar deck so that the cards are in a random order. Each deck is placed face down next to its owner's library. All plane cards remain in the command zone throughout the game, both while they're part of a planar deck and while they're face up.