I have been informed that Luqman used to say, "My son, do not seek knowledge to boast before the scholars, to argue with the foolish, or to show off in gatherings." He then mentioned the rest.He also said, Nawfal bin Musahiq narrated to us from Saeed bin Zayd that the Prophet ﷺ said, "The worst form of usury is to wrongfully attack the honor of a Muslim. This bond of kinship is a branch from the Most Merciful, so whoever severs it, Allah forbids Paradise to him."
حدثنا أبو اليمان أنبأنا شعيب
بلغني أن لقمان كان يقول يا بني لا تعلم العلم لتباهي به العلماء أو تماري به السفهاء وترائي به في المجالس فذكره وقال حدثنا نوفل بن مساحق عن سعيد بن زيد عن النبي ﷺ أنه قال من أربى الربا الاستطالة في عرض مسلم بغير حق وإن هذه الرحم شجنة من الرحمن فمن قطعها حرم الله عليه الجنة
Its chain of transmission is sahih, except that the first part of it is a report attributed to Luqman, not a hadith, while the actual hadith is the second part, narrated from Nawfal from Saeed.Abdullah bin Abdul-Rahman bin Abu Husayn, from Banu Nawfal bin Abd Manaf, was among the younger Tabiin, a trustworthy scholar well versed in the rites of pilgrimage. The authors of the six books narrated from him.Nawfal bin Masahiq bin Abdullah al-Akbar bin Makhrama al-Qurashi al-Amiri was a trustworthy Tabii. Bukhari gave his biography in 4/2:108-109 and mentioned this hadith from him, from Hakam, from Shuayb, with his chain of transmission.Regarding "shijnah" meaning kinship, Ibn Athir said it means a relationship intertwined like the intertwining of blood vessels, likened to that figuratively and by extension. The original meaning of "shijnah," with either a kasrah or a dammah, is a branch off one of the branches of a tree.The first part of this hadith is found in Majma al-Zawaid 1:184, where it is said, Ahmad narrated it, and its chain is disconnected as you see, meaning because it comes from Luqman. The second part, which is the actual hadith, is also found there at 8:150, where it is said, Ahmad and Bazzar narrated it, and the narrators of Ahmad's version are the narrators of the sahih, apart from Nawfal bin Masahiq, who is trustworthy. Hakim also narrated it in Mustadrak 4:157, by way of Abu Yaman, from Shuayb.See also 1680, 1681, 1686, 1687, and 2956.