Sayyiduna Buraydah (may Allah be pleased with him) narrates: One day the Prophet (peace and blessings be upon him) came out and called out loudly three times, saying: "O people, do you know what the likeness of me and of you is? (Our likeness) is like a people who fear that an enemy will come upon them, so they send a man to keep watch for them. While he is doing so, he sees the enemy and comes to warn them. He fears that the enemy will reach him before he can warn his people, so he waves his garment, saying: 'O people, (danger) has come upon you! O people, it has come upon you!'" He said this three times.
Imam Ahmad recorded it, and its narrators are the narrators of the Sahih. (Allamah al-Haythami says:) I say: Other hadiths on this subject will come in the chapter on admonitions, if Allah wills.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 3146