وَالشَّمْسِ

وَالشَّمْسِ is a phrase (شِبْهُ الجُمْلَةِ) consisting of a particle of pulling down (a preposition) and a genitive noun

PhraseParticle / NounNoun Particle
شِبْهُ الجُمْلَةِجَارٌ وَمَجْرُوْرٌاسْمٌ مَجْرُوْرٌحَرْفُ جَرٍّ
PhraseCompoundGenitive NounParticle of pulling down/Preposition
  
by the sunوَالشَّمْسِ=الشَّمْسِ+وَ
 by the sunthe sunby
Surah/Below is the only verse in the holy Quran containing the compoundوَالشَّمْسِ
Verse
91-1By the sunوَالشَّمْسِ