When there are four people Al-Adab Al-Mufrad 1170
Arabic hadith text
وَحَدَّثَنِي أَبُو صَالِحٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم مِثْلَهُ، قُلْنَا: فَإِنْ كَانُوا أَرْبَعَةً؟ قَالَ: لا يَضُرُّهُ.
Translation
Ibn 'Umar reported something similar from the Prophet, may Allah bless him and grant him peace. He stated, "We said, 'If there are four?' He said, 'Then it will not harm him.'"