Translation for 17:55

وَرَبُّكَ أَعۡلَمُ بِمَن فِي ٱلسَّمَٰوَٰتِ وَٱلۡأَرۡضِۗ وَلَقَدۡ فَضَّلۡنَا بَعۡضَ ٱلنَّبِيِّـۧنَ عَلَىٰ بَعۡضٖۖ وَءَاتَيۡنَا دَاوُۥدَ زَبُورٗا ٥٥
Your Lord knows best all those in the heavens and the earth. And We have surely favoured some prophets above others, and to David We gave the Psalms.1 

Foot notes

76869

 The reason David is singled out here is because some Jewish authorities at the time of the Prophet (ﷺ) claimed that no scripture had been revealed after Moses. So this verse refutes this claim by referring to the Psalms of David.