"Have they not considered that there is no madness in their companion?" This is a response from Allah to the polytheists regarding their statement to the Prophet that he is insane. He is saying: If they were to reflect, they would know that he is not insane.
"He is but a warner," who warns of the punishment of Allah, "manifest [in his warning]," clarifying [the message] from Allah.
﴿أَو لم يَتَفَكَّرُوا مَا بِصَاحِبِهِمْ مِنْ جنةٍ﴾ وَهَذَا جوابٌ مِنَ اللَّهِ لِلْمُشْرِكِينَ؛ لِقَوْلِهِمْ لِلْنَبِيِّ إِنَّهُ مجنونٌ يَقُولُ: لَوْ تَفَكَّرُوا، لَعَلِمُوا أَنَّهُ لَيْسَ بمجنونٍ.
﴿إِنْ هُوَ إِلا نَذِيرٌ﴾ يُنْذِرُ مِنْ عَذَابِ اللَّهِ ﴿مُبِينٌ﴾ يبين عَن الله.
