Mukhtasar Muslim

It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that one of his sons died at (the place of) Qudayd or ‘Usfan. So he said (to his servant), "O Kurayb! See how many people have gathered (for the funeral prayer)?" Kurayb said, "I went and saw that people had gathered, so I informed him." Sayyiduna Ibn Abbas (may Allah be pleased with them both) said, "In your estimation, are they forty?" I said, "Yes." He said, "Bring out the bier, for I heard the Messenger of Allah (peace and blessings be upon him) say: 'Whenever forty people who do not associate anything with Allah attend the funeral of a Muslim, Allah certainly accepts their intercession for him.'"