Sahih Muslim 2775 a
Ibn Mas'ud reported that there gathered near the House three persons amongst whom two were Quraishi and one was a Thaqafi or two were Thaqafis and one was a Quraishi. They lacked understanding but wore more flesh. One of them said:
Do you think that Allah hears as we speak? The other one said: He does hear when we speak loudly and He does not hear when we speak in undertones, and still the other one said: If He listens when we speak loudly, He also listens when we speak in undertones. It was on this occasion that this verse was revealed:" You did not conceal yourselves lest your ears, your eyes and your skins would stand witness against you" (xli. 22).
حَدَّثَنَا مُحَمَّدُ بْنُ أَبِي عُمَرَ الْمَكِّيُّ، حَدَّثَنَا سُفْيَانُ، عَنْ مَنْصُورٍ، عَنْ مُجَاهِدٍ، عَنْ أَبِي،
 مَعْمَرٍ عَنِ ابْنِ مَسْعُودٍ، قَالَ اجْتَمَعَ عِنْدَ الْبَيْتِ ثَلاَثَةُ نَفَرٍ قُرَشِيَّانِ وَثَقَفِيٌّ أَوْ ثَقَفِيَّانِ وَقُرَشِيٌّ
 قَلِيلٌ فِقْهُ قُلُوبِهِمْ كَثِيرٌ شَحْمُ بُطُونِهِمْ فَقَالَ أَحَدُهُمْ أَتَرَوْنَ اللَّهَ يَسْمَعُ مَا نَقُولُ وَقَالَ الآخَرُ
 يَسْمَعُ إِنْ جَهَرْنَا وَلاَ يَسْمَعُ إِنْ أَخْفَيْنَا وَقَالَ الآخَرُ إِنْ كَانَ يَسْمَعُ إِذَا جَهَرْنَا فَهُوَ يَسْمَعُ
 إِذَا أَخْفَيْنَا ‏.‏ فَأَنْزَلَ اللَّهُ عَزَّ وَجَلَّ ‏{‏ وَمَا كُنْتُمْ تَسْتَتِرُونَ أَنْ يَشْهَدَ عَلَيْكُمْ سَمْعُكُمْ وَلاَ أَبْصَارُكُمْ
 وَلاَ جُلُودُكُمْ‏}‏ الآيَةَ ‏.‏