Null Profusion

If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Spellbook (an artifact that says you have no maximum hand size) onto the battlefield and then put Null Profusion onto the battlefield, your maximum hand size will be two. However, if those permanents entered in the opposite order, you would have no maximum hand size.

Wotc — October 01, 2009

The triggered ability will trigger when you play a land card or cast a nonland card as a spell. It won't trigger when you play a copy of a card, such as with Isochron Scepter.

Wotc — February 01, 2007

Your maximum hand size is checked only during the cleanup step of your turn. At any other time, you may have any number of cards in hand.

Wotc — February 01, 2007

Countering a spell that has been cast will not prevent you from drawing the card.

Wotc — February 01, 2007