Tafseer Ibn Kathir of AL QASHASH [49]

قُلْ فَأْتُوا بِكِتَابٍ مِّنْ عِندِ اللَّهِ هُوَ أَهْدَى مِنْهُمَا أَتَّبِعْهُ إِن كُنتُمْ صَادِقِينَ

Say, "Then bring a scripture from Allah which is more guiding than either of them that I may follow it, if you should be truthful."