Is Karona's Zealot legal in Standard, Modern, and Commander?

Karona's Zealot is legal in: Legacy, Vintage, Commander.

What type of card is Karona's Zealot?

Karona's Zealot is a Creature — Human Cleric. Its oracle text reads: "Morph {3}{W}{W} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When this creature is turned face up, all damage that would be dealt to it this turn is dealt to target creature instead."