Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates this saying of the Prophet (peace and blessings be upon him): "Whoever conceals any matter of knowledge that he knows will be bridled with a bridle of fire on the Day of Resurrection." He says: This (that is, what is meant by it) is testimony which a person holds; then he is called to give that testimony or is not called, but he has knowledge of the matter, and yet he does not guide the person concerned with that testimony towards it. So what is meant here is having knowledge of this matter.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator, Ibrahim bin Ayyub al-Firsani, and he is majhul (unknown).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العلم / 742
Hadith Gradingمحدثین:إسنادہ ضعیف
Hadith Takhrij«أخرجه المعجم الكبير للطبراني برقم: 10845»