'Abd Allaah ibn 'Umar said,
"'Umar ibn al-Khattab went along with the Prophet (صلى الله علیه وسلم) and a group of people to Ibn Sayyaad, and found him playing with some children near the battlement of Banoo Maghaalah. At that time Ibn Sayyaad was on the threshold of adolescence; he did not realise that anybody was near until the Prophet (صلى الله علیه وسلم) struck him on the back. The Prophet (صلى الله علیه وسلم) said to him: 'Do you bear witness than I am the Messenger of Allaah?' Ibn Sayyaad looked at him and said, 'I bear witness that you are the Prophet (صلى الله علیه وسلم) of the unlettered.' Then Ibn Sayyaad said to the Prophet (صلى الله علیه وسلم), 'Do you bear witness that I am the Messenger of Allaah?' The Prophet (صلى الله علیه وسلم) dismissed this and said, 'I believe in Allaah and His Messengers.' Then the Prophet (صلى الله علیه وسلم) asked him, 'What do you see?' Ibn Sayyaad said, 'Sometimes a truthful person comes to me, and sometimes a liar.' The Prophet (صلى الله علیه وسلم) said to him, 'You are confused', then he said, 'I am hiding something from you.' Ibn Sayyaad said, 'It is Dukh.' The Prophet (صلى الله علیه وسلم) said, 'Silence! You will not be able to go beyond your rank.' 'Umar ibn al-Khattab said, 'O Messenger of Allaah, shall I cut off his head?' The Prophet (صلى الله علیه وسلم) said, 'If he is (the Dajjaal) you will not be able to overpower him, and if he is not, then killing will not do you any good.' "
Saleem ibn 'Abd Allaah said,
"I heard 'Abd Allaah ibn 'Umar say, 'After that, the Prophet (صلى الله علیه وسلم) and Ubayy ibn Ka'b went along to the palm trees where Ibn Sayyaad was. The Prophet (صلى الله علیه وسلم) started to hide behind a tree, with the intention of hearing something from Ibn Sayyaad before Ibn Sayyaad saw him. The Prophet (صلى الله علیه وسلم) saw him lying on a bed, murmuring beneath a blanket. Ibn Sayyaad's mother saw the Prophet (صلى الله علیه وسلم) hiding behind a tree, and said to her son, "O Saf (Ibn Sayyaad's first name), here is Muhammad!" Ibn Sayyad jumped up, and the Prophet (صلى الله علیه وسلم) said, "If you had left him alone, he would have explained himself." "
"Abd Allaah ibn'Umar said, The Prophet (صلى الله علیه وسلم) stood up to address the people. He praised Allaah as He deserved to be praised, then he spoke about the Dajjaal: 'I warn you against him; there is no Prophet who has not warned his people against him, even Noah warned his people against him. But I will tell you something which no other Prophet has told his people. You must know that the Dajjaal is one-eyed, and Allaah is not one-eyed.' "
Ibn Shihaab said:
"'Umar ibn Thaabit al-Ansaaree told me that some of the Companions of the Prophet (صلى الله علیه وسلم) told him that on the day when he warned the people about the Dajjaal, the Prophet (صلى الله علیه وسلم) said: 'There will be written between his eyes the word Kaafir (unbeliever). Everyone who resents his bad deeds - or every believer - will be able to read it.' He also said, 'You must know that no one of you will be able to see his Lord until he dies.' " [Muslim, Bukhaaree] 
Ibn 'Umar said,
"The Prophet (صلى الله علیه وسلم) mentioned the Dajjaal to the people. He said, 'Allaah is not one-eyed, but the Dajjaal is blind in his right eye, and his eye is like a floating grape.' " [Muslim] 
Anas ibn Malik said,
"TheProphet (صلى الله علیه وسلم) said, 'There has never been a Prophet who did not warn his people against that one-eyed liar. Verily he is one-eyed and your Lord is not one-eyed. On his forehead will be written the letter Kaf, Fa, Ra (Kaafir).' " [Muslim, Bukhaaree] 
"The Prophet (صلى الله علیه وسلم) said, 'I know more about the powers which the Dajjaal will have than he will know himself. He will have two flowing rivers: one will appear to be pure water, and the other will appear to be flaming fire. Whosoever lives to see that, let him choose the river which seems to be fire, then let him close his eyes, lower his head and drink from it, for it will be cold water. The Dajjaal will be one-eyed; the place where one eye should be will be covered by a piece of skin. On his forehead will be written the word Kaafir,and every believer, whether literate or illiterate, will be able to read it.' " [Muslim] 
Abu Hurayrah said,
"The Prophet (صلى الله علیه وسلم) said, 'Shall I tell you something about the Dajjaal which no Prophet has ever told his people before me? The Dajjaal is one-eyed and will bring with him something which will resemble Paradise and Hell; but that which he calls Paradise will in fact be Hell. I warn you against him as Noah warned his people against him.' " [Bukhaaree, Muslim] 
Muhammad ibn Munkadir said:
"I saw Jaabir ibn 'Abd Allaah swearing by Allaah that Ibn Sayyaad was the Dajjaal, so I asked him, 'Do you swear by Allaah?' He said, 'I heard 'Umar swear to that effect in the presence of the Prophet (صلى الله علیه وسلم), and the Prophet (صلى الله علیه وسلم) did not disapprove of it.' " 
Some 'ulamaa' (scholars) say that some of the Sahaabah (Companions of the Prophet) believed Ibn Sayyaad to be the greater Dajjaal, but that is not the case: Ibn Sayyaad was a lesser dajjal.
Ibn Sayyaad travelled between Makkah and Madeenah with Abu Sa'eed, and complained to him about the way that people were saying that he was the Dajjaal. Then he said to Abu Sa'eed,
"Did not the Prophet (صلى الله علیه وسلم) say that the Dajjaal would not enter Madinah? I was born there. Did not he say that he would not have any children? - I have children. Did not he say that he would be a Kaafir? - I have embraced Islaam. Of all the people, I know the most about him: I know where he is now. If I were given the opportunity to be in his place, I would not resent it.' " [Bukhaaree, Muslim]
There are many Ahaadeeth about Ibn Sayyaad, some of which are not clear as to whether he was the Dajjaal or not. We shall see Ahaadeeth which indicates that the Dajjaal is not Ibn Sayyaad, as in the Hadeeth of Faatimah Bint Qays al-Fahriyyah, although this does not mean that he was not one of the lesser Dajjaal; but Allaah knows best.
 Bukhaaree, Kitaab al-Adab, 8/49, 50. Muslim, Kitaab al-Fitan, 8/192, 193.
Ibn Sayyaad's [or Ibn Sa'eed's] first name was Saaf. He had some characteristics similar to those ascribed to the Dajjaal. When he was young, he was like a Kaahin (soothsayer) - sometimes he spoke the truth, sometimes he lied. When he grew up, he embraced Islaam and displayed some good characteristics, but later he changed, and it was said that his behaviour might indicate that he was the Dajjaal. But the Prophet (صلى الله علیه وسلم) had not received any Wahy (revelation) to that effect, so he told 'Umar: "If he is [the Dajjaal] you will not be able to overpower him."
Banoo Maghaalah: if you stand facing the Masjid al-Nabawee, (the Prophet's Mosque in Madeenah), everything on your right is the territory of Banoo Maghaalah.
Dukh: i.e. al-Dukhaan (smoke). The Prophet (صلى الله علیه وسلم) was thinking of the Aayah,
"Then wait you for the Day when the sky will bring forth a visible smoke." [ad-Dukhaan (44):10]
"... with the intention of hearing something..." in other words, the Prophet (صلى الله علیه وسلم) wanted to eavesdrop on Ibn Sayyaad so that he and his companions could find out whether he was a soothsayer (kaahin) or a sorcerer.
"if you had left him alone, he would have had explained himself": i.e., if his mother had not told him that the Prophet (صلى الله علیه وسلم) was there, then the Prophet (صلى الله علیه وسلم) would have found out what he was - a soothsayer or a sorcerer.
 Muslim, Kitaab al-Fitan, 8/194, 195.
"His eye is like a floating grape" - this means that, his eye will protrude and there will be some kind of brightness in it.
 Muslim, ibid. Bukhaaree, Kitaab al-Fitan, 9/75, 76.
"On his forehead will be written the letters Kaaf, Faa', Raa' " - this indicates that he will call people to Kufr, not the right path, so we must avoid him. The fact that Muslims will be able to identify him as a Kaafir is a great blessing from Allaah to this Ummah.
 Muslim, ibid. Shorter version in Bukhaaree, Kitaab al-Fitan, 9/75.
 Bukhaaree, Kitaab al-Anbiyaa, 4/75. Muslim, Kitaab al-Fitan, 8/196.
 Muslim, Kitaab al-Fitan, 8/192.