قُلْ يَٰٓأَيُّهَا ٱلنَّاسُ إِنَّمَآ أَنَا۠ لَكُمْ نَذِيرٌ مُّبِينٌ · فَٱلَّذِينَ ءَامَنُوا۟ وَعَمِلُوا۟ ٱلصَّٰلِحَٰتِ لَهُم مَّغْفِرَةٌ وَرِزْقٌ كَرِيمٌ · وَٱلَّذِينَ سَعَوْا۟ فِىٓ ءَايَٰتِنَا مُعَٰجِزِينَ أُو۟لَٰٓئِكَ أَصْحَٰبُ ٱلْجَحِيمِ
Qul yā ayyuha'n-nāsu innamā ana lakum nadhīrun mubīn · Fa'lladhīna āmanū wa ʿamilu'ṣ-ṣāliḥāti lahum maghfiratun wa rizqun karīm · Wa'lladhīna saʿaw fī āyātinā muʿājizīna ulāʾika aṣḥābu'l-jaḥīm
"Say: 'O people! I am to you only a clear warner.' Those who believe and do righteous deeds shall have forgiveness and a noble provision. But those who run about among Our signs, seeking to frustrate them are the companions of the blaze."
And the pattern of the sentence must be recorded: innamā — the particle of restriction (ḥaṣr). "Only, nothing but."
I record this as a grammatical observation: in the forty-seventh verse it was said yastaʿjilūnaka bi'l-ʿadhāb — "they ask you to hasten the punishment". The forty-ninth verse corrects the addressee of that demand: bringing punishment is not the warner's business. The particle of restriction does exactly this work.
The same limit was treated at al-Furqān 25/43 (a-fa-anta takūnu ʿalayhi wakīlā), and was recorded there as a "limit of responsibility". I rely on that treatment.
In Form III (mufāʿala), muʿājiz: "one who strives to render powerless". The word therefore conveys not a failure but an effort to make something fail.
The construct is worth recording, and I give this as an observation: the verse does not say "those who deny the signs". It says "those who run about among Our signs" — the verb, that is, is a verb of motion. Denial is described as a work done at a run, not sitting down.
And this makes a link with the forty-sixth verse: there we had a-fa-lam yasīrū fi'l-arḍ — "have they not travelled in the land?" Two verbs of motion in two verses: one required, the other censured. The same energy, in two separate directions.