Al-Kāfi

Hadith 1683
fear-of-god
11ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنْ عَبْدِ الله بْنِ الْمُغِيرَةِ عَنْ إِسْمَاعِيلَ الْبَجَلِيِّ عَنْ أَبِي عَبْدِ الله (عَلَيهِ السَّلام) قَالَ إِنْ لَمْ يَجِئْكَ الْبُكَاءُ فَتَبَاكَ فَإِنْ خَرَجَ مِنْكَ مِثْلُ رَأْسِ الذُّبَابِ فَبَخْ بَخْ.
11. Ali ibn Ibrahim has narrated from his father from ‘Abd Allah ibn al-Mughirah from Isma’Il al-Bajilli from Abu ‘Abdillah (a.s.) who has said the following: “If weeping does not come through, make a weeping-like face. If of the size of the head of a fly tears come out that is your sheer good luck indeed.”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī