Divine Smite — ruling 1

An attacking or blocking creature that phases out is removed from combat.

Divine Smite — ruling 2

Phasing out doesn't cause any “leaves the battlefield” abilities to trigger. Similarly, phasing in won't cause any “enters the battlefield” abilities to trigger.

Divine Smite — ruling 3

Phased out permanents are treated as though they don't exist. They can't be the target of spells or abilities, their static abilities have no effect on the game, their triggered abilities can't trigger, they can't attack or block, and so on.

Divine Smite — ruling 4

As a creature is phased out, Auras and Equipment attached to it also phase out at the same time. Those Auras and Equipment will phase in at the same time that creature does, and they'll phase in still attached to that creature.

Divine Smite — ruling 5

Permanents phase back in during their controller's untap step, immediately before that player untaps their permanents. Creatures that phase in this way are able to attack and pay a cost of {T} during that turn. If a permanent had counters on it when it phased out, it will have those counters when it phases back in.

Divine Smite — ruling 6

Any continuous effects with a “for as long as” duration, such as that of Mind Flayer, ignore phased-out objects. If ignoring those objects causes the effect's conditions to no longer be met, the duration will expire.

Divine Smite — ruling 7

Choices made for permanents as they entered the battlefield are remembered when they phase in.

Divine Smite — ruling 8

If an opponent gains control of your nonblack creature, you phase it out with Divine Smite, and the duration of the control-change effect expires before it phases back in, your creature phases in under your control as that opponent's next untap step begins. If they leave the game before their next untap step, it phases in as the next untap step begins after their turn would have begun.

Divine Smite : règles, fonctionnement et interactions (MTG)

Divine Smite is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Target creature or planeswalker an opponent controls phases out. If that permanent is black, exile it instead. (If it phases out, treat it and anything attached to it as though they don't exist until its controller's next turn.)

How it works : Divine Smite

Original English text — Wizards of the Coast / Scryfall

#1July 23, 2021· Wizards of the Coast
An attacking or blocking creature that phases out is removed from combat.
No other card is named in this ruling.
#2July 23, 2021· Wizards of the Coast
Phasing out doesn't cause any “leaves the battlefield” abilities to trigger. Similarly, phasing in won't cause any “enters the battlefield” abilities to trigger.
No other card is named in this ruling.
#3July 23, 2021· Wizards of the Coast
Phased out permanents are treated as though they don't exist. They can't be the target of spells or abilities, their static abilities have no effect on the game, their triggered abilities can't trigger, they can't attack or block, and so on.
No other card is named in this ruling.
#4July 23, 2021· Wizards of the Coast
As a creature is phased out, Auras and Equipment attached to it also phase out at the same time. Those Auras and Equipment will phase in at the same time that creature does, and they'll phase in still attached to that creature.
No other card is named in this ruling.
#5July 23, 2021· Wizards of the Coast
Permanents phase back in during their controller's untap step, immediately before that player untaps their permanents. Creatures that phase in this way are able to attack and pay a cost of during that turn. If a permanent had counters on it when it phased out, it will have those counters when it phases back in.
No other card is named in this ruling.
#6July 23, 2021· Wizards of the Coast
Any continuous effects with a “for as long as” duration, such as that of Mind Flayer, ignore phased-out objects. If ignoring those objects causes the effect's conditions to no longer be met, the duration will expire.
No other card is named in this ruling.
#7July 23, 2021· Wizards of the Coast
Choices made for permanents as they entered the battlefield are remembered when they phase in.
No other card is named in this ruling.
#8July 23, 2021· Wizards of the Coast
If an opponent gains control of your nonblack creature, you phase it out with Divine Smite, and the duration of the control-change effect expires before it phases back in, your creature phases in under your control as that opponent's next untap step begins. If they leave the game before their next untap step, it phases in as the next untap step begins after their turn would have begun.
No other card is named in this ruling.