Abu Ahmad ibn Adi al-Jurjani: I searched through many of his hadiths and did not find anything that could be considered weak. He may have made mistakes, or mixed things up, as others do, but he is not bad.
Abu Bakr al-Bayhaqi: His narration is weak if he does not indicate he heard it directly. Once, he said: He can be relied upon in matters where there is no disagreement among the scholars of Hadith.
Abu Hatim al-Razi: I do not consider him strong in Hadith, he is weak in Hadith. He is preferable to me than Aflah ibn Sa'id. I write down his Hadith.
Abu Hatim ibn Hibban al-Busti: There was no one in Medina who came close to Ibn Ishaq in his knowledge, nor equaled him in his collection. He is one of the best people in narrating historical reports. Once, he said: He used to practice Tadlis (concealing the chain of narrators) from weak narrators, so mistakes occurred in his narration because of them. However, if he clarifies that he heard it directly, then he is reliable and his narration can be used as evidence.
Abu Zur'ah al-Dimashqi: A man whom the great scholars of knowledge agreed to take from.
Abu Zur'ah al-Razi: Saduq (truthful).
Abu Mu'awiyah al-Darir: One of the most knowledgeable people.
Abu Ya'la al-Khalili: A scholar with extensive narration and knowledge, trustworthy.
Ahmad ibn Hanbal: Good in Hadith. Once, he said: He is not a proof. Once, he said: If he narrates alone, his Hadith is not accepted. By Allah, I saw him narrating a single Hadith from different groups of people without distinguishing who said what. Once, he said: As for the battles (Maghazi) and similar things, it can be written down. As for what is lawful and unlawful, it needs something like this - and he stretched out his hand and clasped his fingers. Once, he said: He practiced Tadlis a lot, but he was among the best.
Ahmad ibn Shu'ayb al-Nasa'i: Not strong.
Ahmad ibn Salih al-Jili: Trustworthy.
Ibrahim ibn Ya'qub al-Jawzajani: People admire his Hadith, and he was accused of things other than lying.
Ibn Hajar al-'Asqalani: The Imam of Maghazi (Prophet's battles), Saduq, he practiced Tadlis, and was accused of Shiism and Qadariyyah. Once, he said: An Imam in Maghazi, there are differences of opinion regarding relying on him, and the majority are in favor of accepting him in the Sirah (biography). I investigated those who criticized him and it became clear that the reason was not discrediting.
Ibn Shihab al-Zuhri: Knowledge will remain in Medina as long as this one (Ibn Ishaq) is in it.
Al-Khatib al-Baghdadi: He defended him vigorously. More than one scholar refrained from relying on the narrations of Ibn Ishaq for reasons including: he was inclined towards Shiism, he was accused of Qadariyyah, and he practiced Tadlis in his Hadith. As for his truthfulness, it is not denied.
Al-Daraqutni: The Imams differed regarding him, and the most knowledgeable of them about him was Malik. He is not a proof, he is only considered. Once, he said: He is not relied upon.
Al-Dhahabi: The Imam was truthful, from the seas of knowledge. He said in Tadhhib: He is not that precise, so his Hadith falls short of the rank of Sahih (sound). He is truthful in himself, but ill. One of the prominent Imams, he saw Anas and Sa'id ibn al-Musayyab.
Hamad ibn Salamah al-Basri: Had it not been for the necessity, I would not have narrated from Muhammad ibn Ishaq.
Sufyan al-Thawri: The leader of the believers in Hadith.
Sufyan ibn 'Uyainah: I have been accompanying Ibn Ishaq for seventy years, and no one from the people of Medina accuses him or says anything about him. Once, he said: They accused him of Qadariyyah.
Sulaiman ibn Tarkhan al-Taymi: He accused him of lying.
Sulaiman ibn Mihran al-A'mash: Liar.
Shubah ibn al-Hajjaj: The leader of the Hadith scholars in his memorization. Once, he said: The leader of the believers in Hadith, and one of the best people in narrating historical reports and the best of them in memorizing their texts. Once, he said: Truthful in Hadith.
Ali ibn al-Madini: He relied on his Hadith and said: His Hadith is Sahih (sound). Once, he said: I only found two Munkar (rejected) Hadiths from him. He mentioned him in the questions of Uthman ibn Muhammad ibn Abi Shaybah and said: He is righteous and moderate. Once, he said: No one criticized Muhammad ibn Ishaq except for the Hadith of Nafi' from Ibn Umar from the Prophet (peace and blessings of Allah be upon him): When one of you feels sleepy... Once, he said: Saduq. Once, he said: Trustworthy. Once, he said: ...
Malik ibn Anas: A liar from the liars. Once, he said: We expelled him from Medina. Once, he said: He accused him. Once, he said: He criticized him.
Muhammad ibn Ibrahim al-Bawshanji: Trustworthy, trustworthy.
Muhammad ibn Idris al-Shafi'i: Whoever wants to delve into the Maghazi (Prophet's battles), he is dependent on Muhammad ibn Ishaq.
Muhammad ibn Sa'd, the scribe of al-Waqidi: Trustworthy, and some people criticize him. Once, he said: Knowledge will remain abundant in Medina as long as Ibn Ishaq is among them. Once, he said: Abundant knowledge will remain in Hijaz as long as this one-eyed (Ibn Ishaq) is among them.
Muhammad ibn Abdullah al-Makhrami: We found him to be truthful - three times.
Muhammad ibn Abdullah ibn al-Barqi: I have not seen the scholars of Hadith disagreeing about his trustworthiness, the goodness of his Hadith and his narration. There is some discussion about his narration from Nafi'.
Muhammad ibn Abdullah ibn Numayr: If he narrates from well-known people he heard from, then he is good in Hadith, truthful. He was criticized because he narrates fabricated Hadiths from unknown people.
Muhammad ibn Yahya al-Dhuhali: Good in Hadith, he has some strange narrations.
Al-Nūr al-Dīn al-Haythami: He practiced Tadlis, and he is trustworthy.
Hisham ibn 'Urwah al-Qurashi: He criticized him. Once, he said: He is a liar. Once, he said: When did Muhammad ibn Ishaq hear from Fatimah bint al-Mundhir, and when did he enter upon her?
Wahib ibn Khalid: He accused him of lying.
Yahya ibn Sa'id al-Qattan: Liar. Once, he said: I deliberately left him and did not write any Hadith from him at all. Once, he said: He criticized him.
Yahya ibn Ma'in: Trustworthy, and he was good in Hadith. Once, he said: He is not like that, weak. Once, he said: He is, in my opinion, sick, not strong. Once, he said: Trustworthy, but not a proof. Once, he said: I do not like to rely on him in matters of inheritance. Once, he said: People have always been cautious of his Hadith. Once, he said: Truthful, but he is not a proof.
Yazid ibn Harun al-Ayli: If I had the authority, I would have appointed Ibn Ishaq as the leader of the Hadith scholars.