Послание пришло утром.

Because послание is a neuter singular noun.

In Russian past tense, the verb agrees with the subject in gender and number:

• masculine: пришел
• feminine: пришла
• neuter: пришло
• plural: пришли

So:

• письмо пришло — the letter/message came
• весть пришла — the news came
• послание пришло — the message/epistle came

The ending -о in пришло shows that the subject is neuter.

Послание means message, missive, or sometimes epistle.

Compared with some other Russian words:

• сообщение = message, notice, text message, communication
• письмо = letter
• послание = a message sent to someone, often a bit more formal, literary, or elevated

So this sentence may sound slightly more literary than everyday speech. In casual modern Russian, a learner will often hear сообщение or письмо more often, depending on context.

Because Russian often uses certain time expressions in the instrumental case without a preposition to mean at/in that part of the day.

So:

• утром = in the morning
• днем = in the daytime / during the day
• вечером = in the evening
• ночью = at night

This is a very common pattern. Even though English needs in the morning, Russian can simply say утром.

Утром is the instrumental case of утро.

Base form:

• утро = morning

Instrumental form:

• утром

In this sentence, it is being used adverbially, meaning it functions like a time adverb: in the morning.

So although instrumental often means with or by means of, it also appears in fixed time expressions like this.

Yes — this is completely natural in Russian.

Just like English can say:

• The message came in the morning
• A letter arrived in the morning

Russian also treats things like letters, news, and messages as things that arrive:

• письмо пришло
• сообщение пришло
• послание пришло

So прийти / приходить is not only for people physically walking somewhere. It is also used for things that are delivered, received, or reach someone.

Пришло is the past tense of the perfective verb прийти.

That matters because perfective usually presents the action as a completed whole. Here, the idea is that the message arrived — the event happened and is complete.

Compare:

• пришло = it came / it arrived
• приходило = it used to come / it was coming / it would come repeatedly, depending on context

In this sentence, the speaker is referring to one completed event, so пришло is the natural choice.

Yes. Russian word order is flexible, and changing it usually changes the focus or emphasis, not the basic meaning.

For example:

• Послание пришло утром. — neutral; the message came in the morning.
• Утром пришло послание. — emphasis on when it came.
• Послание утром пришло. — possible, but more marked in tone.

So the original sentence is a very normal, neutral way to say it.

Because Russian has no articles.

English distinguishes:

• a message
• the message

Russian usually leaves that to context.

So послание can mean:

• a message
• the message

depending on the situation. If the meaning is already known from context, Russian does not need an article to show it.

The stress is:

• послАние
• пришлО
• Утром

So the sentence is pronounced roughly like:

pa-SLA-ni-ye pri-shLO U-tram

A few notes:

• послание has four syllables: по-сла-ни-е
• пришло is stressed on the last syllable
• утром is stressed on the first syllable

Learning stress is important in Russian because it is not always predictable from spelling.