(50) باب لاَ يَتَنَاجَى اثْنَانِ دُونَ الثَّالِثِ
It was narrated that Ibn 'Umar said:
"The Messenger of Allah(ﷺ) forbade two to converse (privately) to the exclusion of a third."
Reference: Sunan Ibn Majah 3776
In-book reference: Book 33, Hadith 121
English translation: Vol. 5, Book 33, Hadith 3776