Translation of an ayah from Surati Aali 'Imran - 8

Please translate the following from Surati Aali 'Imraan searching any new verbs/nouns that have not yet been encountered. Please provide any additional explanation where you see necessary.


لِمَ تَكْفُرُونَ بِآيَاتِ اللَّهِ وَاللَّهُ شَهِيدٌ عَلَىٰ مَا تَعْمَلُونَ


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بسم الله الرحمن الرحيم

لِمَ - Why
تَكْفُرُونَ - (do) you disbelieve
بِآيَاتِ - in the verses
اللَّهِ - of Allah
وَاللَّهُ - and/though Allah
شَهِيدٌ - is a witness
عَلَىٰ - upon
مَا - what
تَعْمَلُونَ - you practice*

لِمَ تَكْفُرُونَ بِآيَاتِ اللَّهِ وَاللَّهُ شَهِيدٌ عَلَىٰ مَا تَعْمَلُونَ
Translation: 'Why do you disbelieve in the verses of Allah, and/though Allah is a witness upon what you practice.'

* I think here it is emphasising that Allah is all-knowing and all-seeing of your disbelief, and also to the extent of your belief.