﴿ سَلْهُمْ أَيُّهُم بِذَٰلِكَ زَعِيمٌ ﴾

“Ask them which of them is able to vouch for this!”

Ask them which of them will aver will guarantee for them that? that decision which they have made for themselves namely that they will be given better reward than the believers in the Hereafter?