عَنْ حَمْزَةَ بْنِ حُمْرَانَ عَنْ اَبِي عَبْدِ اللهِؑ قَالَ لَوْ لَمْ يَكُنْ فِي الْاَرْضِ اِلَّا اثْنَانِ لَكَانَ اَحَدُهُمَا الْحُجَّةَ وَ لَوْ ذَهَبَ اَحَدُهُمَا بَقِيَ الْحُجَّة
Hamzah Ibn Humraan reports that Imam Abu Abdillah (al-Sadeq a.s.) said, “If there remained only two people in the earth, certainly one of them would be a divine proof. If one of them perished, the divine proof would remain.”
References:
1. Behaar al-Anwaar, vol. 23, p. 43, Chapter 1, H. 85
2. Kamaal al-Deen, vol. 1, p. 232, Chapter 22, H. 38