لِيَعْبُدُوْا

لِيَعْبُدُوْا is a verbal sentence (الجُمْلَةُ الفِعْلِيَّةُ) consisting of an accusative particle and an accusative present tense verb

The natural state of the present tense verb is يَعْبُدُوْنَ however due to the presence of the accusative particle لِ that precedes it, it loses its last letter ن and changes to يَعْبُدُوْا

SentenceParticle / VerbVerb Particle
الجُمْلَةُ الفِعْلِيَّةُحَرْفُ النَّصْبِ وَفِعْلُ النَّصْبِفِعْلٌ مُضَارِعٌ مَنْصُوْبٌ بِحَذْفِ النُّوْنِحَرْفُ النَّصْبِ
verbal sentenceSentencea present or future tense accusative verban accusative particle
  
to worshipلِيَعْبُدُوْا=يَعْبُدُوْا+لِ
to worshipthey worshipto
Surah/Below are the 2 verses in the holy Quran containing the verbal sentenceلِيَعْبُدُوْا
Verse
They have taken their rabbis and their monks as their Lords from other than Allah (SWT)اتَّخَذُوا أَحْبَارَهُمْ وَرُهْبَانَهُمْ أَرْبَابًا مِّنْ دُوْنِ اللهِ
and the Messiah, son of Maryam and not were they commanded but to worship One Godوَالمَسِيْحَ ابْنَ مَرْيَمَ وَمَآ أُمِرُوا إِلَّا لِيَعْبُدُوا إِلَاهًا وَاحِدًا
9-31there is no God except Him, Glory be to Him over what they associateلَّا إِلَاهَ إِلَّا هُوَ سُبْحَانَهُ عَمَّا يُشْرِكُوْنَ
And not were they commanded except to worship Allah (SWT) being sincere to Himوَمَآ أُمِرُوْا إِلَّا لِيَعْبُدُوْا اللهَ مُخْلِصِيْنَ لَهُ
the upright religion and to establish the prayerالدِّيْنَ حُنَفَآءَ وَيُقِيْمُوْا الصَّلَاةَ
98-5and to give the charity (obligatory tax) and that is the correct religionوَيُؤْتُوْا الزَّكَاةَ وَذَلِكَ دِيْنُ القَيِّمَةِ