Saeed Maqburi reported,

I sat down with Ibn Umar while a man was speaking with him privately. As I joined them, he struck my chest with his hand and said, "Do you not know that the Messenger of Allah ﷺ said, 'When two people are conversing privately, do not sit with them until you ask their permission'?"

حدثنا سريج حدثنا عبد الله

عن سعيد المقبري قال

جلست إلى ابن عمر ومعه رجل يحدثه فدخلت معهما فضرب بيده صدري وقال أما علمت أن رسول الله ﷺ قال إذا تناجى اثنان فلا تجلس إليهما حتى تستأذنهما