In one narration the wording is: "The people of the tribe of Mudar will not leave any believing servant of Allah Almighty except that they will either subject him to trial or kill him."
Ahmad recorded it with various chains and al-Bazzar through various routes, and in some of them the wording is: "Sayyiduna Hudhayfah (may Allah be pleased with him) said: O people of the tribe of Mudar! Come near. By Allah! You will continue to subject every believer to trial and to kill him, until Allah Almighty, His angels and the believers strike you, to the extent that you will not be able to defend even the low end of a valley. The people said: When this is our state, then why have you put us forward? He replied: The reason is that from among you came the leader of the children of Adam (peace be upon him), and from among you came those who outstrip others, just like the horses that come out ahead in a race."
Al-Tabarani recorded it in al-Mu'jam al-Awsat in abridged form; the narrators of one of the chains of Ahmad and one of the chains of al-Bazzar are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الفتن - أعاذنا الله منها / 12390