Musnad Ahmad 1163:43

Abu Ubaydah Abd al-Wahid al-Haddad narrated to us, he said: al-Hakam ibn Farrukh Abu Bakkar narrated to us, that Abu al-Malih went out for a funeral. When he stood [in position], they thought he was going to say the takbir, so he turned and said: "Stand straight so that your intercession may be accepted, for if I were to choose a man, I would have chosen this one. Beware, for indeed, Abdullah ibn Sulayt narrated to me, from one of the Mothers of the Believers, who is Maymunah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: 'There is no Muslim upon whom a group (ummah) of people prays, except that they intercede for him.'" He said: So I asked Abu al-Malih about the "group" (ummah), and he said: "Forty."