From Sahih Bukhari (Hadith 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
Reference: Bukhari 3060