مَثَلُ الْفَرِيقَيْنِ
The likeness of the two parties,
This refers to those disbelievers whom Allah first described as wretched, and then those believers whom He described with delightfulness.
كَالَاعْمَى وَالَاصَمِّ وَالْبَصِيرِ وَالسَّمِيعِ
The likeness of the two parties is as the blind and the deaf and the seer and the hearer.
The first group is like one who is blind and deaf, while the second group is like he who sees and hears.
Thus, the disbeliever is blind from the truth in this life and in the Hereafter. He is not guided to goodness, nor does he recognize it. He is deaf from hearing the proofs, thus he does not hear that which would benefit him.
As Allah says,
وَلَوْ عَلِمَ اللَّهُ فِيهِمْ خَيْرًا لَاسْمَعَهُمْ
Had Allah known of any good in them, He would indeed have made them listen. (8;23)
The believer is smart, bright and clever. He sees the truth and distinguishes between the truth and falsehood. Thus, he follows the good and abandons the evil. He hears and distinguishes between the proof and scepticism. Therefore, falsehood does not overcome him.
هَلْ يَسْتَوِيَانِ مَثَلً
Are they equal when compared!
ie are these two types of people alike!
أَفَلَ تَذَكَّرُونَ
Will you not then take heed!
This statement means, "Will you not consider, so that you may distinguish between these two categories of people."
This is as Allah mentions in another verse,
لَا يَسْتَوِى أَصْحَـبُ النَّارِ وَأَصْحَـبُ الْجَنَّةِ أَصْحَـبُ الْجَنَّةِ هُمُ الْفَأيِزُونَ
Not equal are the dwellers of the Fire and the dwellers of the Paradise. It is the dwellers of Paradise that will be successful. (59;20)
Allah also says,
وَمَا يَسْتَوِى الاٌّعْمَى وَالْبَصِيرُ
وَلَا الظُّلُمَاتُ وَلَا النُّورُ
وَلَا الظِّلُّ وَلَا الْحَرُورُ
وَمَا يَسْتَوِى الاٌّحْيَأءُ وَلَا الاٌّمْوَاتُ إِنَّ اللَّهَ يُسْمِعُ مَن يَشَأءُ وَمَأ أَنتَ بِمُسْمِعٍ مَّن فِى الْقُبُورِ
إِنْ أَنتَ إِلاَّ نَذِيرٌ
إِنَّأ أَرْسَلْنَـكَ بِالْحَقِّ بَشِيراً وَنَذِيراً وَإِن مِّنْ أُمَّةٍ إِلاَّ خَلَ فِيهَا نَذِيرٌ
Not alike are the blind and the seeing. Nor are (alike) darkness and light. Nor are (alike) the shade and the sun's heat. Nor are (alike) the living and the dead.
Verily, Allah makes whom He wills to hear, but you cannot make hear those who are in graves. You are only a warner.
Verily, We have sent you with the truth, a bearer of glad tidings and a warner. And there never was a nation but a warner had passed among them. (35;19-24