"The People of the Scripture ask you to bring down to them a book from the heaven," meaning: specifically for them. "But they had asked of Moses greater than that and said, 'Show us Allah outright,'" meaning: visibly. "And We gave Moses clear authority," meaning: a manifest proof.
﴿يَسْأَلُكَ أَهْلُ الْكِتَابِ أَنْ تُنَزِّلَ عَلَيْهِم كتابا من السَّمَاء﴾ أَي: خَاصَّة عَلَيْهِم ﴿فَقَدْ سَأَلُوا مُوسَى أَكْبَرَ مِنْ ذَلِكَ فَقَالُوا أرنا الله جهرة﴾ أَي: عيَانًا ﴿وَآتَيْنَا مُوسَى سُلْطَانًا مُبينًا﴾ حجَّة (بَيِّنَة).