Sayyiduna Nahik bin Suraym al-Sakuni (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "You will certainly fight the polytheists, until those of you who remain will fight the Dajjal at the river Jordan, you being on its eastern side and he on its western side." The narrator says: I do not know where on earth the Jordan was at that time.
Al-Tabarani and al-Bazzar recorded it, and the narrators of al-Bazzar are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الفتن - أعاذنا الله منها / 12542