Fruitful Harvest

If you have below 20 life the you can't untap this card during your untap phase.
{t}: Gain {w} or {g}.
{3}{w}{t}: Choose one -
Gain 3 life.
Prevent the next 4 damage that would be dealt to target creature of player this turn.
You may play both of these effects from your hand, for free, as an instant: If you do Exile this card.