Al-Kāfi

2. A number of our people have narrated from Ahmad ibn Muhammad ibn Khalid from Muhammad ibn Ali from Yunus ibn Ya’qub from ‘Abd al-‘Ala’ from Abu ‘Abdillah (a.s.) who has said the following:“Abu ‘Abd Allah (a.s.) has said, ‘Whenever a group (of forty) people come together for a matter to pray and plead before Allah for help, when they disperse their prayer will be accepted.’”