Oath of Mages — ruling 1

The ability can only target an opponent of the current player.

Oath of Mages — ruling 2

The targeted player having more life than the current player is a part of the targeting requirement. A player can’t be targeted by this ability unless it’s true, and the ability doesn’t resolve if it’s no longer true at that time.

Oath of Mages : règles, fonctionnement et interactions (MTG)

Oath of Mages 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

At the beginning of each player's upkeep, that player chooses target player who has more life than they do and is their opponent. The first player may have this enchantment deal 1 damage to the second player.

How it works : Oath of Mages

Original English text — Wizards of the Coast / Scryfall

#1October 1, 2009· Wizards of the Coast
The ability can only target an opponent of the current player.
No other card is named in this ruling.
#2October 1, 2009· Wizards of the Coast
The targeted player having more life than the current player is a part of the targeting requirement. A player can’t be targeted by this ability unless it’s true, and the ability doesn’t resolve if it’s no longer true at that time.
No other card is named in this ruling.