Al-Kāfi

Hadith 1786
dua
5ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ هِشَامِ بْنِ سَالِمٍ عَنْ أَبِي عَبْدِ الله (عَلَيهِ السَّلام) قَالَ مَنْ قَدَّمَ أَرْبَعِينَ مِنَ الْمُؤْمِنِينَ ثُمَّ دَعَا اسْتُجِيبَ لَهُ.
5. Ali ibn Ibrahim has narrated from his father from Ibn Abi ‘Umayr from Hisham ibn Salim from Abu ‘Abdillah (a.s.) who has said the following: “Abu ‘Abd Allah (a.s.) has said, ‘Whoever prays for forty believing persons and then for himself, his prayer will be accepted.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī