Jubayr bin Nufayr narrates from his father that the Messenger of Allah (peace and blessings be upon him) mentioned the Dajjal and said: "If he (the Dajjal) emerges while I am present, then I will be the one who contends with him on your behalf; and if he emerges after me, then every person will be his own defender, and Allah is my successor (guardian) over every Muslim. Beware! He is one-eyed, as if his eye were like the eye of Abd al-Uzza bin Qatan al-Khuza'i. Take heed! Between his two eyes will be written 'Kafir' (disbeliever), which every Muslim will read. So whoever of you meets him should recite the opening verses of Surah al-Kahf. He will emerge from the route between Syria and Iraq and will spread great mischief to the right and to the left. O servants of Allah, remain steadfast!" He (peace and blessings be upon him) said this three times. It was said: O Messenger of Allah! How long will he stay on the earth? He (peace and blessings be upon him) said: "Forty days: one day like a year, one day like a month, one day like a week, and the rest of the days will be like your ordinary days." The Companions said: O Messenger of Allah! How shall we pray on that (long) day? Will the prayers of a single day suffice, or shall we estimate the time? He (peace and blessings be upon him) said: "No, rather you should estimate (the time)." This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.