ENOfficial
Abu Sa'id al-Khudri reported God's messenger as saying, "The dajjal will be followed by seventy thousand of my people wearing dark cloaks." It is transmitted in Sharh as-sunna.
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «يَتْبَعُ الدَّجَّالَ مِنْ أُمَّتِي سَبْعُونَ أَلْفًا عَلَيْهِمُ السِّيجَانُ» . رَوَاهُ فِي " شرح السّنة
sunnah.com