Chafetz Chaim, Part Two, The Prohibition Against Rechilut, Principle 3
Can copy this into an AI, or connect the whole library to your assistant. For deeper learning, you can directly use the original seforim, sites, and apps.
אִם רְאוּבֵן דִּבֵּר עַל שִׁמְעוֹן בִּפְנִי לֵוִי, וְהָלַךְ לֵוִי וְסִפֵּר הַדְּבָרִים לְשִׁמְעוֹן, אָסוּר לְשִׁמְעוֹן לוֹמַר אַחַר כָּךְ לִרְאוּבֵן: אֵיךְ דִּבַּרְתָּ עָלַי בִּפְנִי לֵוִי? כִּי עַל יְדֵי זֶה (ג) גַּם הוּא עוֹבֵר עַל אִסוּר רְכִילוּת מֵחֲמַת לֵוִי, וַאֲפִלּוּ אִם לֹא יַזְכִּיר לוֹ בְּפֵרוּשׁ אֶת שֵׁם לֵוִי, וְיֹאמַר לוֹ סְתָם: שֶׁשָּׁמַעְתִּי שֶׁדִּבַּרְתָּ עָלַי כָּךְ וְכָךְ, אִם עַל יְדֵי זֶה (ד) מִמֵּילָא יָבִין רְאוּבֵן, מִי הָיָה הַמְגַלֶּה לוֹ, אָסוּר. וּבַעֲוֹנוֹתֵינוּ הָרַבִּים, הַרְבֵּה אֲנָשִׁים נִכְשָׁלִין בָּזֶה.
If Reuven spoke against Shimon before Levi, and Levi went and told this to Shimon, it is forbidden for Shimon to say afterwards to Reuven: "How did you speak against me before Levi!" For in doing so, he [Shimon] also transgresses the prohibition of rechilut because of [his mentioning of] Levi, even if he does not explicitly mention Levi's name, but simply says [to Reuven]" "I heard that you said this and this about me" — If through this, Reuven will naturally understand who revealed it to him, it is forbidden. And in our many sins, many go astray in this.