The Messenger of Allah ﷺ forbade two people from conversing privately to the exclusion of a third when no one else is with them. The Prophet ﷺ also forbade a man from taking another man's seat, saying, "If he returns, he has the greater right to it."
حدثنا يزيد أخبرنا محمد بن إسحاق عن نافع
نهى رسول الله ﷺ أن يتناجى اثنان دون الثالث إذا لم يكن معهم غيرهم قال ونهى النبي ﷺ أن يخلف الرجل الرجل في مجلسه وقال إذا رجع فهو أحق به
Its isnad is sahih. The first part of it is a repetition of 4685, see also 4871. The second part is in Majma al-Zawaid 8:61, where it says, Ahmad and Bazzar narrated it, and its narrators are trustworthy, except that Ibn Ishaq practiced tadlis.This criticism of Ibn Ishaq has been repeated from him many times, without evidence. Ibn Ishaq was only spoken against following Malik and others, and they found no genuine flaw in him. The claim of his tadlis only arose in connection with what he narrates of mursal and disconnected reports in biography and military campaign literature. For this reason Bukhari, in Tarikh al-Kabir 40/1/1, gave his biography without mentioning any discrediting of him. Rather, he narrated from Ibn Madini, from Ibn Uyayna, that Zuhri said, "Whoever wants the military campaigns, let him go to the client of Qays bin Makhrama," meaning Ibn Ishaq. Ibn Uyayna said, "I have not seen anyone accuse Ibn Ishaq." Zuhri was Ibn Ishaq's teacher, and he praised him with this praise.Then Bukhari said, Ubayd bin Yaish told me, I heard Yunus bin Bukayr say, I heard Shuba say, "Muhammad bin Ishaq is the commander of the hadith scholars in his memorization." Nothing beyond this counts as testimony and validation.In Tahdheeb it says that Abu Zura Dimashqi said, "Ibn Ishaq is a man upon whom the great scholars have agreed to rely, and the hadith scholars tested him and found honesty and goodness in him," along with Ibn Shihab's praise of him.I discussed Malik's statement about him with Duhaym, and he considered that it was not about hadith at all, but rather because Malik accused him regarding predestination. I say, rather it was because there was some estrangement and rivalry between the two of them, so each of them spoke against the other, while both of them are trustworthy authorities, may Allah have mercy on them both.