The Belligerent — ruling 1

Once The Belligerent's triggered ability resolves, you can look at the top card of your library whenever you want until end of turn (with one restriction; see below), even if you don't have priority. This action doesn't use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.

The Belligerent — ruling 2

If the top card of your library changes while you're casting a spell, playing a land, or activating an ability, you can't look at the new top card until you finish doing so. This means that if you cast a spell from the top of your library, you can't look at the next one until you're done paying for that spell.

The Belligerent — ruling 3

If the top card of your library has an Adventure, you can cast the Adventure spell this way.

The Belligerent — ruling 4

You must pay all costs and follow all timing rules for spells cast and lands played from the top of your library this way.

The Belligerent : règles, fonctionnement et interactions (MTG)

The Belligerent 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

Whenever The Belligerent attacks, create a Treasure token. Until end of turn, you may look at the top card of your library any time, and you may play lands and cast spells from the top of your library. Crew 3

How it works : The Belligerent

Original English text — Wizards of the Coast / Scryfall

#1November 10, 2023· Wizards of the Coast
Once The Belligerent's triggered ability resolves, you can look at the top card of your library whenever you want until end of turn (with one restriction; see below), even if you don't have priority. This action doesn't use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.
No other card is named in this ruling.
#2November 10, 2023· Wizards of the Coast
If the top card of your library changes while you're casting a spell, playing a land, or activating an ability, you can't look at the new top card until you finish doing so. This means that if you cast a spell from the top of your library, you can't look at the next one until you're done paying for that spell.
No other card is named in this ruling.
#3November 10, 2023· Wizards of the Coast
If the top card of your library has an Adventure, you can cast the Adventure spell this way.
No other card is named in this ruling.
#4November 10, 2023· Wizards of the Coast
You must pay all costs and follow all timing rules for spells cast and lands played from the top of your library this way.
No other card is named in this ruling.