"The Messenger of Allah said: 'Whoever is asked about knowledge that he has and he conceals it, will be bridled on the Day of Resurrection with reins of fire.'" (Using translation from Ibn Mājah 266)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ مَنْ سُئِلَ عَنْ عِلْمٍ يَعْلَمُهُ فَكَتَمَهُ أُلْجِمَ يَوْمَ الْقِيَامَةِ بِلِجَامٍ مِنْ نَارٍ