وَذَلِكُمْ ظَنُّكُمُ الَّذِي ظَنَنتُم بِرَبِّكُمْ أَرْدَاكُمْ
but you thought that Allah knew not much of what you were doing. And that thought of yours which you thought about your Lord, has brought you to destruction;
meaning, `this evil thought, i.e., your belief that Allah did not know much of what you were doing, is what has caused you to be doomed and has made your losers before your Lord.'
فَأَصْبَحْتُم مِّنْ الْخَاسِرِينَ
and you have become of those utterly lost!
means, `in the place of Resurrection, you have lost your own selves and your families.'
Imam Ahmad recorded that Abdullah, may Allah be pleased with him, said,
"I was hiding beneath the covering of the Ka`bah, and three men came along -- a man from the Quraysh and two of his brothers-in-law from Thaqif, or a man from Thaqif and two of his brothers-in-law from the Quraysh. Their bellies were very fat, and did not have much understanding. They said some words I could not hear, then one of them said,
`Do you think that Allah can hear what we are saying now?'
The other said, `If we raise our voices, He will hear it, but if we do not raise our voices, He will not hear it.'
The other said, `If He can hear one thing from us, He can hear everything.'
I mentioned this to the Prophet , then Allah revealed the words;
وَمَا كُنتُمْ تَسْتَتِرُونَ أَنْ يَشْهَدَ عَلَيْكُمْ سَمْعُكُمْ وَلَا أَبْصَارُكُمْ وَلَا جُلُودُكُمْ
(And you have not been hiding yourselves (in the world), lest your ears and your eyes and your skins should testify against you) until;
مِّنْ الْخَاسِرِينَ
(of those utterly lost!).
This is how it was recorded by At-Tirmidhi.
A similar report was also narrated by Ahmad (through a different chain),
Muslim and At-Tirmidhi, and Al-Bukhari and Muslim also recorded (a different chain).
فَإِن يَصْبِرُوا فَالنَّارُ مَثْوًى لَّهُمْ
وَإِن يَسْتَعْتِبُوا فَمَا هُم مِّنَ الْمُعْتَبِينَ