لِّلْمُصَلِّيْنَ

لِّلْمُصَلِّيْنَ is a phrase ( شِبْهُ الجُمْلَةِ) consisting of a preposition and a genitive noun

PhraseParticle / NounNoun Particle
شِبْهُ الجُمْلَةِ=جَارٌ وَمَجْرُوْرٌ=اسْمٌ مَجْرُوْرٌ+حَرْفُ جَرٍّ
PhraseCompoundGenitive NounParticle of pulling down
  
to the worshippers=لِّلْمُصَلِّيْنَ=المُصَلِّيْنَ+لِّ
to those who praythose who prayto
Surah/Below is the only verse in the holy Quran containing the compoundلِّلْمُصَلِّيْنَ
Verse
107-4So, woe to those who prayفَوَيْلٌ لِّلْمُصَلِّيْنَ