user10105: Is there a rule where if a monk is an arahant and if he is to tell he is an arahant, he can only say it to a Upasampada monk and not even a samanera monk?
If so, please provide the source of the rule

user24052: A monk can only relate his actual attainment of a superior human state to:

another monk (bhikkhu), or
a nun (bhikkhunī).

In other words, he commits an offense if he relates it to, e.g., a novice (samanera).
Since he told the truth, however, he won't be expelled — he's still considered a bhikkhu — but as @ruben2020 mentioned: he should confess the offense to another bhikkhu.

The factors for the full offense here are two:

Effort: One reports one’s actual attainment of a superior human state

Object: to an unordained person, i.e., any human being who is not a bhikkhu or bhikkhunī.



Source

user471: According to the Patimokkha rules:


Should any bhikkhu, without direct knowledge, claim a superior human state, a truly noble knowledge and vision, as present in
  himself, saying, "Thus do I know; thus do I see," such that regardless
  of whether or not he is cross-examined on a later occasion, he — being
  remorseful and desirous of purification — might say, "Friends, not
  knowing, I said I know; not seeing, I said I see — vainly, falsely,
  idly," unless it was from over-estimation, he also is defeated and no
  longer in affiliation.
Should any bhikkhu report (his own) superior human state to an unordained person, when it is factual, it is to be confessed.


But above, there are no distinctions made between fully ordained monks and novice monks.

10105: <p>Is there a rule where if a monk is an arahant and if he is to tell he is an arahant, he can only say it to a Upasampada monk and not even a samanera monk?</p>

<p>If so, please provide the source of the rule</p>
 24052: <p>A monk can only relate his actual attainment of a superior human state to:</p>
<ul>
<li>another monk (bhikkhu), or</li>
<li>a nun (bhikkhunī).</li>
</ul>
<p>In other words, he commits an offense if he relates it to, e.g., a novice (samanera).</p>
<p>Since he told the truth, however, he won't be expelled — he's still considered a bhikkhu — but as @ruben2020 mentioned: he should confess the <a href="https://www.dhammatalks.org/vinaya/bmc/Section0016.html#Pc8" rel="nofollow noreferrer">offense</a> to another bhikkhu.</p>
<blockquote>
<p>The factors for the full offense here are two:</p>
<ol>
<li><p>Effort: One reports one’s actual attainment of a superior human state</p>
</li>
<li><p>Object: to an unordained person, i.e., any human being who is not a bhikkhu or bhikkhunī.</p>
</li>
</ol>
</blockquote>
<p><a href="https://www.dhammatalks.org/vinaya/bmc/Section0016.html#Pc8" rel="nofollow noreferrer">Source</a></p>
 471: <p>According to the <a href="https://www.accesstoinsight.org/tipitaka/vin/sv/bhikkhu-pati-intro.html" rel="nofollow noreferrer">Patimokkha rules</a>:</p>

<blockquote>
  <ul>
  <li><p>Should any bhikkhu, without direct knowledge, claim a superior human state, a truly noble knowledge and vision, as present in
  himself, saying, "Thus do I know; thus do I see," such that regardless
  of whether or not he is cross-examined on a later occasion, he — being
  remorseful and desirous of purification — might say, "Friends, not
  knowing, I said I know; not seeing, I said I see — vainly, falsely,
  idly," unless it was from over-estimation, he also is defeated and no
  longer in affiliation.</p></li>
  <li><p>Should any bhikkhu report (his own) superior human state to an unordained person, when it is factual, it is to be confessed.</p></li>
  </ul>
</blockquote>

<p>But above, there are no distinctions made between fully ordained monks and novice monks.</p>
