Jalal Abdulrub on the Unreliablity of Ibn Ishaq Jalal Abdulrub explains the problems of Ibn Ishaq (the earliest biographer of Prophet Muhammad) and explains some of our greatest scholars have condemned Ibn Ishaq's
3 Adh-Dhahabi also listed some of the major scholars of Islam who refuted Ibn Is`haq's reliability in Hadith narrations. Imam Malik, for instance, called Ibn Is`haq a liar and Yahya Ibn Sa`eed al-Ansari, as well as, al-A`mash refuted one of Ibn Is`haq's narrations by saying that he lied. As a general statement, Yahya Ibn Sa`eed graded Ibn Ishaq as being weak in Hadith narration. Imam Ahmad Ibn Hanbal discounted the reliability of Ibn Ishaq if he alone narrates a Hadith. Also, Imams Yahya Ibn Ma`een (in another narration from him), an-Nasaii and ad-Daraqutni stated that Ibn Ishaq was weak in Hadith. The great Imam of Sunnah, Imam Ahmad Ibn Hanbal, also added that Ibn Ishaq's narrations are not accepted if they are about the Sunan (Pl. for Sunnah; [yet, Craig Ibn Winn claims that Ibn Is`haq's Seerah is a Sunnah book!]), stating that even [in the rare occasions] where Ibn Is`haq clearly stated that he heard a Hadith from his teacher, he would often contradict other narrators. Therefore, and as Imam A`hmad stated, if Ibn Is`haq alone reports a Hadith, then that narration is not accepted. Adh-Dhahabi also stated that if a narration that Ibn Is`haq reports contradicts other [more established] narrators, then Ibn Is`haq's narration is rejected.
4 Adh-Dhahabi listed some of the reasons why Ibn Is`haq was considered weak regarding Hadith narration, as follows:
A) Imam A`hmad Ibn Hanbal stated that Ibn Is`haq was a Mudallis [Ibn Is`haq often started his narrations by saying, Those whom I trust narrated to me, or Some men from this city told me , etc. He also would collect Hadith s from unreliable narrators and hide the name of his teacher by saying, So and So said, meaning the teacher of his teacher, who may be trustworthy, so that the Hadith narration is not rejected if the name of his own teacher is specified. However, whenever Ibn Ishaq said, So and so said to me, he would not lie.] , and in another occasion, he said that Ibn Ishaq's Tadlees (v. for Mudallis) was substantial. Imam Ahmad also said that Ibn Ishaq did not care from whom he collected Hadith.
B) Imam Ibn Numair said that Ibn Ishaq reported false Hadith s from unknown narrators.
C) Adh-Dhahabi concluded by saying that among the worst errors made by Ibn Is`haq is that he used to record narrations he collected from anyone, and thus, did not have Wara`  in this regard, may Allah forgive him.
5 How Ibn Ishaq's narration should be treated is summarized in this statement from Imam Ibn Numair, If he narrates a Hadith from teachers he directly heard from and who are known to be truthful, then his Hadith is from the grade Hasan because he is truthful. Yet, Imam Ahmad stated that if Ibn Ishaq is the only narrator of that Hadith, then his narration is discounted. And the key words to look for here, for Ibn Ishaq's narration not to be dismissed outright, are, If Ibn Ishaq says, So and so narrated to me', then he did hear that narration.' Otherwise, if he says, So and so said', then the narration is rejected.' Meaning, Ibn Ishaq would not lie; if he states that he heard the Hadith from his teacher, then his assertion is accepted. (Shaykh Jalal Abu Al Rub, The Prophet of Mercy, Chapter 2, page 10)