He reported from his father Kaab bin Malik that whenever he heard the call to prayer on Friday, he would invoke mercy upon Saad bin Zurara. So I asked him, "Whenever you hear the call to prayer, you invoke mercy upon Saad bin Zurara?"He replied, "Because he was the first to gather us for the Friday prayer at Hazm an-Nabit in the lava field of Banu Bayadah, at a marsh called Naqi al-Khasamat."I asked, "How many of you were there that day?"He answered, "Forty."
-، عن أبيه كعب بن مالك، أنه كان إذا سمع النداء يوم الجمعة ترحم لأسعد بن زرارة، فقلت له: إذا سمعت النداء ترحمت لأسعد بن زرارة؟ قال: لأنه أول من جمع بنا في هزم النبيت من حرة بني بياضة، في نقيع يقال له: نقيع الخصمات. قلت: كم أنتم يومئذ؟ قال: أربعون.
Abu Dawud (1070) and Ibn Majah (1082) both narrated it through Muhammad bin Ishaq, from Muhammad bin Abu Umama bin Sahl bin Hunayf, from his father, from Abdul-Rahman bin Kaab bin Malik, who related it. Its chain of transmission is hasan because of Ibn Ishaq, for he is truthful but practices tadlis, though he explicitly stated that he heard it directly in other narrations, as will be mentioned later. Ibn Khuzayma (1724) and Hakim (1/281) both graded it sahih, both through Muhammad bin Ishaq, who said, "Muhammad bin Abu Umama narrated to me." Hakim said, "Sahih according to the criterion of Muslim."As for what was narrated from Umm Abdullah Dawsiyyah, as a marfu report, "Jumuah is obligatory upon every village, even if there are only four people in it," and in another wording, "Only three, the fourth of them being their imam." This is daif. Daraqutni narrated it (2/8) and explained its weakness, saying, "It contains Walid bin Muhammad Muqari, who is discarded."Likewise, what was narrated from Abu Umama as a marfu report, "Jumuah is due upon fifty, and there is nothing due below that," is not sound. Daraqutni narrated it through Jafar bin Zubayr, from Qasim bin Abdul-Rahman, and said, "Jafar bin Zubayr is discarded."Likewise, what was narrated from Jabir bin Abdullah, who said, "It has been the established practice that every three have an imam, and every forty and above have Jumuah, and Eid al-Adha, and Eid al-Fitr, because they constitute a congregation," is not sound. Daraqutni narrated it through Abdul-Aziz bin Abdul-Rahman, who said, Khaseef narrated to us, from Ata bin Abu Rabah, from Jabir, relating the same. Abdul-Aziz bin Abdul-Rahman Balisi was described by Imam Ahmad, who said, "Strike out his hadiths, they are fabrications," or he said, "forgeries." See Jarh wa Tadil (5/388). His teacher Khaseef was declared daif by a group of the scholars.