Surah Al-Hajj 22:21
وَلَهُم مَّقَـٰمِعُ مِنْ حَدِيدٍ
And for [striking] them are maces of iron.
Translation: Saheeh International
Tafsir
And there will be hooked rods of iron for them for their heads to be beaten with.
Excerpt from Tafsir al-Jalalayn, commentary on 22:21, via Quran.com. The reader has the full commentary and 9 more tafsirs.