Al-Adab Al-Mufrad, Book 47, Hadith 1172 (In-Book) ⓘ
Ibn 'Umar said, "When there are four, there is no harm."
حَدَّثَنَا قَبِيصَةُ، قَالَ: حَدَّثَنَا سُفْيَانُ، عَنِ الأَعْمَشِ، عَنْ أَبِي صَالِحٍ، عَنِ ابْنِ عُمَرَ قَالَ: إِذَا كَانُوا أَرْبَعَةً فَلا بَأْسَ.
also referenced under: Hadith 1172 (Reference) & Book 47, Hadith 1172 (English)