Sahih Muslim 2014 b
This hadith is reported on the authority of Laith b. Sa'd with the same chain of transmitters, but with a slight variation in wording (and that is that) he (the Holy Prophet) said:
There is a day in a year when descends the pestilence; at the end of the hadith Laith said that the non Arabs save themselves from it in Kanun Awwal (this is the month of December).
وَحَدَّثَنَا نَصْرُ بْنُ عَلِيٍّ الْجَهْضَمِيُّ، حَدَّثَنِي أَبِي، حَدَّثَنَا لَيْثُ بْنُ سَعْدٍ، بِهَذَا الإِسْنَادِ
 ‏.‏ بِمِثْلِهِ غَيْرَ أَنَّهُ قَالَ ‏
"‏ فَإِنَّ فِي السَّنَةِ يَوْمًا يَنْزِلُ فِيهِ وَبَاءٌ ‏"‏ ‏.‏ وَزَادَ فِي آخِرِ الْحَدِيثِ
 قَالَ اللَّيْثُ فَالأَعَاجِمُ عِنْدَنَا يَتَّقُونَ ذَلِكَ فِي كَانُونَ الأَوَّلِ ‏.‏