("Of what benefit to you was your gathering...") meaning, your great numbers,
("...and your arrogance") This Ayah means, your great numbers and wealth did not save you from Allah's torment. Rather, you are dwelling in His torment and punishment. `Ali bin Abi Talhah reported from Ibn `Abbas,
(Are they those, of whom you swore that Allah would never show them mercy) refers to the people of Al-A`raf who will be told when Allah decrees:
((Behold! It has been said to them): "Enter Paradise, no fear shall be on you, nor shall you grieve.")