And whenever there comes down a Surah, they look at one another (saying);"Does any one see you!" Then they turn away. Allah has turned their hearts because they are a people that understand not.
This describes the hypocrites that when a Surah is revealed to the Messenger of Allah,
نَّظَرَ بَعْضُهُمْ إِلَى بَعْضٍ
(they look at one another), they turn their heads, right and left, saying,
هَلْ يَرَاكُم مِّنْ أَحَدٍ ثُمَّ انصَرَفُواْ
("Does any one see you!" Then they turn away. ..) turning away from, and shunning the truth.
This is the description of hypocrites in this life, for they do not remain where the truth is being declared, neither accepting nor understanding it, just as Allah said in other Ayat,
فَمَا لَهُمْ عَنِ التَّذْكِرَةِ مُعْرِضِينَ
كَأَنَّهُمْ حُمُرٌ مُّسْتَنفِرَةٌ
فَرَّتْ مِن قَسْوَرَةٍ
Then what is wrong with them that they turn away from admonition As if they were wild donkeys. Fleeing from a lion. (74;49-51)
and,
فَمَالِ الَّذِينَ كَفَرُواْ قِبَلَكَ مُهْطِعِينَ
عَنِ الْيَمِينِ وَعَنِ الشِّمَالِ عِزِينَ
So what is the matter with those who disbelieve that they hasten to hear from you. (Sitting) in groups on the right and on the left. (70;36-37)
This Ayah also means, what is the matter with these people who turn away from you to the right and to the left, to escape from truth and revert to falsehood.
Allah's statement,
ثُمَّ انصَرَفُواْ صَرَفَ اللّهُ قُلُوبَهُم
Then they turn away. Allah has turned their hearts (from Truth) is similar to,
فَلَمَّا زَاغُواْ أَزَاغَ اللَّهُ قُلُوبَهُمْ
So when they turned away, Allah turned their hearts away. (61;5).
Allah said next,
بِأَنَّهُمْ قَوْمٌ لاَّ يَفْقَهُون
because they are a people that understand not.
They neither understand Allah's Word nor attempt to comprehend it nor want it. Rather, they are too busy, turning away from it. This is why they ended up in this condition