Al-Qasim bin al-Mutayyab narrated that Abu al-Malih al-Hudhali (may Allah have mercy on him) went out to a funeral. When the deceased was placed on the bier, he turned to the people and said: Straighten your rows and make your intercession good. Then Abu al-Malih said: Abdullah bin Salit narrated to me - he was the brother of the Mother of the Believers Maymunah (may Allah be pleased with her) - from Sayyidah Maymunah (may Allah be pleased with her), from the Prophet (peace and blessings be upon him), that he (peace and blessings be upon him) said: "Whoever has the funeral prayer offered over him by an ummah (a group of people), their intercession for their brother is accepted."
An ummah means forty to a hundred, an 'usbah means ten to forty, and a nafar means three to ten people.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20410