Sneak Attack

Oracle Text

R: You may put a creature card from your hand onto the battlefield. That creature gains haste. Sacrifice the creature at the beginning of the next end step.

Card Rulings

5/1/2007 Putting the card onto the battlefield is optional. When the ability resolves, you can choose not to.
6/8/2016 You only sacrifice the creature if you still control it at end of turn. If that creature has left the battlefield, even if it came back, you don’t sacrifice it. Likewise, if an opponent has gained control of it, it won’t be sacrificed and will remain on the battlefield indefinitely.
6/8/2016 Putting a card onto the battlefield is optional. When the ability resolves, you can choose not to, even if you have one in your hand.

Additional Information