Al-Kāfi
Hadith 16173ـ وَبِإِسْنَادِهِ قَالَ قَالَ النَّبِيُّ (صَلَّى اللهُ عَلَيْهِ وآلِه) أَ لا أَدُلُّكُمْ عَلَى سِلاحٍ يُنْجِيكُمْ مِنْ أَعْدَائِكُمْ وَيُدِرُّ أَرْزَاقَكُمْ قَالُوا بَلَى قَالَ تَدْعُونَ رَبَّكُمْ بِاللَّيْلِ وَالنَّهَارِ فَإِنَّ سِلاحَ الْمُؤْمِنِ الدُّعَاءُ.
3. Through his chain of narrators the narrator has said the following: “The Holy Prophet (a.s.) once said, ‘Should I guide you to a weapon that will save you from your enemies and increase your means of living?’ They said, ‘Yes, (O Messenger of Allah).’ The Holy Prophet said, ‘Pray and plead before Allah for help night and day; prayer is the weapon of believing people.’”