The Messenger of Allah ﷺ said, "Whoever is asked about knowledge and conceals it will be bridled on the Day of Resurrection with a bridle of fire."
قال رسول الله ﷺ: من سئل عن علم ثم كتمه ألجم يوم القيامة بلجام من نار.
Narrated by Abu Dawud (3658), Tirmidhi (2649), and Ibn Majah (261), all of them through various chains from Ali bin Hakam, from Ataa (who is Ibn Abu Rabah), from Abu Hurairah, and he mentioned it. Tirmidhi said, "A hasan hadith."I say, this is because Tirmidhi narrated it through the route of Umara bin Zazan Saydalani, who is disputed but is hasan al-hadith. It has been corroborated, as Abu Dawud, Ahmad (2/263), and Ibn Hibban (95) narrated it through various chains from Hammad bin Salama, from Ali bin Hakam Banani, with his chain, in similar fashion.Hakim narrated it (1/101) through another route from Ataa and said, "This is a hadith that people have circulated through many chains, which can be collected and studied together. This chain is sahih according to the criteria of the two shaykhs (Bukhari and Muslim)."However, Hakim also said, "I discussed this chapter with Abu Ali Hafiz (who is Husayn bin Ali), then I asked him, does any of these chains from Ataa hold up as sahih? He said, No. I said, Why not? He said, Because Ataa did not hear it from Abu Hurairah."Then Hakim mentioned several routes for this hadith and presented them to his teacher, who approved of them and acknowledged them to him. Hakim then said, "When I gathered together the material on this chapter, I found a group who mentioned that Ataa heard it from Abu Hurairah, and we found the hadith with a sahih chain free of any objection."