Allah's Apostle told us a long narrative about Ad-Dajjal, and among the many things he mentioned, was his saying, "Ad-Dajjal will come and it will be forbidden for him to pass through the entrances of Medina. He will land in some of the salty barren areas (outside) Medina; on that day the best man or one of the best men will come up to him and say, 'I testify that you are the same Dajjal whose description was given to us by Allah's Apostle .' Ad-Dajjal will say to the people, 'If I kill this man and bring him back to life again, will you doubt my claim?' They will say, 'No.' Then Ad-Dajjal will kill that man and bring him back to life. That man will say, 'Now I know your reality better than before.' Ad-Dajjal will say, 'I want to kill him but I cannot.' "
Once Allah's Apostle stood amongst the people, glorified and praised Allah as He deserved and then mentioned the Dajjal saying, "l warn you against him (i.e. the Dajjal) and there was no prophet but warned his nation against him. No doubt, Noah warned his nation against him but I tell you about him something of which no prophet told his nation before me. You should know that he is one-eyed, and Allah is not one-eyed."
Narrated Muhammad bin Al-Munkadir:
I saw Jabir bin 'Abdullah swearing by Allah that Ibn Sayyad was the Dajjal. I said to Jabir, "How can you swear by Allah?" Jabir said, "I have heard 'Umar swearing by Allah regarding this matter in the presence of the Prophet and the Prophet did not disapprove of it."
'Abdullah reported on the authority of his father 'Umar b. Khattab that he heard from the Messenger of Allah (may peace he upon him) say: I was sleeping when I saw myself making circuit around the Ka'bah, and I saw there a man of fair complexion with straight hair between two men. Water was flowing from his head or water was falling from his head. I said: Who is he? They answered: He is the son of Mary. Then I moved forward and cast a glance and there was a bulky man of red complexion with thick locks of hair on his head, blind of one eye as it his eye was a swollen grape. I asked: Who is he? They said: He is Dajjal. He had close resemblance with Ibn Qatan amongst men.
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: The Last Hour would not come until the Romans would land at al-A'maq or in Dabiq. An army consisting of the best (soldiers) of the people of the earth at that time will come from Medina (to counteract them). When they will arrange themselves in ranks, the Romans would say: Do not stand between us and those (Muslims) who took prisoners from amongst us. Let us fight with them; and the Muslims would say: Nay, by Allah, we would never get aside from you and from our brethren that you may fight them. They will then fight and a third (part) of the army would run away, whom Allah will never forgive. A third (part of the army). which would be constituted of excellent martyrs in Allah's eye, would be killed ani the third who would never be put to trial would win and they would be conquerors of Constantinople. And as they would be busy in distributing the spoils of war (amongst themselves) after hanging their swords by the olive trees, the Satan would cry: The Dajjal has taken your place among your family. They would then come out, but it would be of no avail. And when they would come to Syria, he would come out while they would be still preparing themselves for battle drawing up the ranks. Certainly, the time of prayer shall come and then Jesus (peace be upon him) son of Mary would descend and would lead them in prayer. When the enemy of Allah would see him, it would (disappear) just as the salt dissolves itself in water and if he (Jesus) were not to confront them at all, even then it would dissolve completely, but Allah would kill them by his hand and he would show them their blood on his lance (the lance of Jesus Christ).
Narrated Fatimah, daughter of Qays:
The Apostle of Allah (peace_be_upon_him) once delayed the congregational night prayer.
He came out and said: The talk of Tamim ad-Dari detained me. He transmitted it to me from a man who was on of of the islands of the sea. All of a sudden he found a woman who was trailing her hair. He asked: Who are you?
She said: I am the Jassasah. Go to that castle. So I came to it and found a man who was trailing his hair, chained in iron collars, and leaping between Heaven and Earth.
I asked: Who are you? He replied: I am the Dajjal (Antichrist). Has the Prophet of the unlettered people come forth now? I replied: Yes. He said: Have they obeyed him or disobeyed him? I said: No, they have obeyed him. He said: That is better for them.
Narrated Jabir ibn Abdullah:
The Apostle of Allah (peace_be_upon_him) said one day from the pulpit: When some people were sailing in the sea, their food was finished. An island appeared to them. They went out seeking bread. They were met by the Jassasah (the Antichrist's spy).
I said to AbuSalamah: What is the Jassasah? He replied: A woman trailing the hair of her skin and of her head. She said: In this castle. He then narrated the rest of the (No. 4311) tradition. He asked about the palm-trees of Baysan and the spring of Zughar. He said: He is the Antichrist. Ibn Salamah said to me: There is something more in this tradition, which I could not remember. He said: Jabir testified that it was he who was Ibn Sayyad.
I said: He died. He said: Let him die. I said: He accepted Islam. He said: Let him accept Islam. I said: He entered Medina. He said: Let him enter Medina.

The Story of Ibn Sayyad
{Hadith about Ibn Sayyad, The character whom Caliph Umar(Radiallah Anhu) strongly suspected of being dajjal, strong enough to swear by Allah in the presence of the Prophet(salalahu alaih wasalam). And the prophet(salalahu alaih wasalam) did not object to this)