Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) said: "Two people should not talk privately, leaving out the third, for this hurts the believer, and Allah Almighty dislikes hurting the believer."
Abu Ya'la and al-Tabarani in al-Mu'jam al-Awsat recorded it. The narrators of Abu Ya'la are the narrators of the Sahih, except al-Hasan bin Kathir, whom Ibn Hibban declared thiqah (trustworthy). The name of Abd al-Wahhab bin al-Ward is Wuhayb bin al-Ward, as mentioned by the teacher of the hadith masters (huffaz), al-Mizzi.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 12952