(Ar-Rahman) 55 : 35
يُرْسَلُ عَلَيْكُمَا شُوَاظٌ مِنْ نَارٍ وَنُحَاسٌ فَلَا تَنْتَصِرَانِ
A flame of fire and a molten brass will be sent upon both of you; then both of you won’t be helped.
In Heaven, barricades are there to not pass the boundary, and are protected with a special type of flames and liquids. They may be cosmic rays, meteors, nebulae, etc. See explanation 15: 18; and 37: 9-10.