Sahih al-Bukhari 3060
Narrated Hudhaifa:
The Prophet (ﷺ) said (to us), " List the names of those people who have announced that they are 
Muslims." So, we listed one thousand and five hundred men. Then we wondered, "Should we be 
afraid (of infidels) although we are one thousand and five hundred in number?" No doubt, we 
witnessed ourselves being afflicted with such bad trials that one would have to offer the prayer alone 
in fear.


Narrated Al-A`mash:

"We (listed the Muslims and) found them five hundred." 
And Abu Muawiya said, "Between six hundred to seven hundred."
حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، حَدَّثَنَا سُفْيَانُ، عَنِ الأَعْمَشِ، عَنْ أَبِي وَائِلٍ، عَنْ حُذَيْفَةَ ـ رضى الله عنه ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏
"‏ اكْتُبُوا لِي مَنْ تَلَفَّظَ بِالإِسْلاَمِ مِنَ النَّاسِ ‏"‏‏.‏ فَكَتَبْنَا لَهُ أَلْفًا وَخَمْسَمِائَةِ رَجُلٍ، فَقُلْنَا نَخَافُ وَنَحْنُ أَلْفٌ وَخَمْسُمِائَةٍ فَلَقَدْ رَأَيْتُنَا ابْتُلِينَا حَتَّى إِنَّ الرَّجُلَ لَيُصَلِّي وَحْدَهُ وَهْوَ خَائِفٌ‏.‏   
حَدَّثَنَا عَبْدَانُ، عَنْ أَبِي حَمْزَةَ، عَنِ الأَعْمَشِ، فَوَجَدْنَاهُمْ خَمْسَمِائَةٍ‏.‏ قَالَ أَبُو مُعَاوِيَةَ مَا بَيْنَ سِتِّمِائَةٍ إِلَى سَبْعِمِائَةٍ‏.‏