Al-Adab Al-Mufrad #1175
Behaviour with people
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
حَدَّثَنَا قَبِيصَةُ، قَالَ: حَدَّثَنَا سُفْيَانُ، عَنِ الأَعْمَشِ، عَنْ أَبِي صَالِحٍ، عَنِ ابْنِ عُمَرَ قَالَ: إِذَا كَانُوا أَرْبَعَةً فَلا بَأْسَ.
Ibn 'Umar said, "When there are four, there is no harm."
About Al-Adab Al-Mufrad
This hadith is #1175 from Al-Adab Al-Mufrad, in the Book of Behaviour with people.