The Dajjal will have the letters K-F-R (kafir) written on his forehead;

Sahih Bukhari

004.055.574 – Narrated Mujahid:

That when the people mentioned before Ibn ‘Abbas that the Dajjal would have the word Kafir, (i.e. unbeliever) or the letters Kafir (the root of the Arabic verb ‘disbelieve’) written on his forehead, I heard Ibn ‘Abbas saying, “I did not hear this, but the Prophet said, ‘If you want to see Abraham, then look at your companion (i.e. the Prophet) but Moses was a curly-haired, brown man (who used to ride) a red camel, the reins of which was made of fires of date-palms. As if I were now looking down a valley.”

A description of Dajjal’s defective right eye;

Sahih Muslim

041.7005 – Ibn Umar reported that Allah’s Messenger (may peace be upon him) made a mention of Dajjal in the presence of the people and said: Allah is not one-eyed and behold that Dajjal is blind of the right eye and his eye would be like a floating grape.

Of Dajjal having the letters K-F-R written between his eyes;

Sahih Muslim

041.7008 – Anas b. Malik reported that Allah’s Messenger (may peace be upon him) said: There would be written three letters k. f. r., i. e. Kafir, between the eyes of the Dajjal.

One of Dajjal’s eyes being blind, and the letters K-F-R written between his eyes, which everyone would be able to read;

Sahih Muslim

041.7009 – Anas b. Malik reported that Allah’s Messenger (may peace be upon him) said: Dajjal is blind of one eye and there is written between his eyes the word” Kafir”. He then spelled the word as k. f. r., which every Muslim would be able to read.

More descriptions of Dajjal’s physical appearance;

Sahih Muslim

041.7010 – Hudhalfa reported that Allah’s Messenger (may peace be upon him) said: Dajjal is blind of left eye with thick hair and there would be a garden and fire with him and his fire would be a garden and his garden would be fire.

A detailed narration regarding an encounter with the Dajjal on an island;

Sahih Muslim

041.7028 – Amir b. Sharahil Sha’bi Sha’b Hamdan reported that he asked Fatima, daughter of Qais and sister of ad-Dahhak b. Qais and she was the first amongst the emigrant women: Narrate to me a hadith which you had heard directly from Allah’s Messenger (may peace be upon him) and there is no extra link in between them. She said: Very well, if you like, I am prepared to do that, and he said to her: Well, do It and narrate that to me. She said: I married the son of Mughira and he was a chosen young man of Quraish at that time, but he fell as a martyr in the first Jihad (fighting) on the side of Allah’s Messenger (may peace be upon him). When I became a widow, ‘Abd al-Rahman b. Auf, one amongst the group of the Companions of Allah’s Messenger (may peace be upon him), sent me the proposal of marriage. Allah’s Messenger (may peace be upon him) also sent me such a message for his freed slave Usama b. Zaid. And it had been conveyed to me that Allah’s Messenger (may peace be upon him) had said (about Usama): He who loves me should also love Usima. When Allah’s Messenger (may peace be upon him) talked to me (about this matter), I said: My affairs are in your hand. You may marry me to anyone whom you like. He said: You better shift now to the house of Umm Sharik, and Umm Sharik was a rich lady from amongst the Anqir. She spent generously for the cause of Allah and entertained guests very hospitably. I said: Well, I will do as you like. He said: Do not do that for Umm Sharik is a woman who is very frequently visited by guests and I do not like that your head may be uncovered or the cloth may be removed from your shank and the strangers may catch sight of them which you abhor. You better shift to the house of your cousin ‘Abdullah b. ‘Amr b. Umm Maktum and he is a person of the Bani Fihr branch of the Quraish, and he belonged to that tribe (to which Fatima) belonged. So I shifted to that house, and when my period of waiting was over, I heard the voice of an announcer making an announcement that the prayer would be observed in the mosque (where) congregational prayer (is observed).

So I set out towards that mosque and observed prayer along with Allah’s Messenger (may peace be upon him) and I was in the row of the women which was near the row of men. When Allah’s Messenger (may peace be upon him) had finished his prayer, he sat on the pulpit smiling and said: Every worshipper should keep sitting at his place. He then said: Do you know why I had asked you to assemble? They said: Allah and His Messenger know best. He said: By Allah. I have not made you assemble for exhortation or for a warning, but I have detained you here, for Tamim Dari, a Christian, who came and accepted Islam, told me something, which agrees with what I was-telling you about the Dajjal. He narrated to me that he had sailed in a ship along with thirty men of Bani Lakhm and Bani Judham and had been tossed by waves in the ocean for a month. Then these (waves) took them (near) the land within the ocean (island) at the time of sunset. They sat in a small side-boat and entered that Island. There was a beast with long thick hair (and because of these) they could not distinguish his face from his back. They said: Woe to you, who can you be? Thereupon it said: I am al-Jassasa. They said: What is al-Jassasa? And it said: O people go to this person in the monastery as he is very much eager to know about you. He (the narrator) said: When it named a person for us we were afraid of it lest it should be a Devil. Then we hurriedly went on till we came to that monastery and found a well-built person there with his hands tied to his neck and having iron shackles between his two legs up to the ankles. We said: Woe be upon thee, who are you? And he said: You would soon come to know about me. But tell me who are you. We said: We are people from Arabia and we embarked upon a boat but the sea-waves had been driving us for one month and they brought as near this island. We got into the side-boats and entered this island and here a beast met us with profusely thick hair and because of the thickness of his hair his face could not be distinguished from his back. We said: Woe be to thee, who are you? It said: I am al- Jassasa. We said: What is al-Jassasa? And it said: You go to this very person in the monastery for he is eagerly waiting for you to know about you. So we came to you in hot haste fearing that that might be the Devil. He (that chained person) said: Tell me about the date-palm trees of Baisan. We said: About what aspect of theirs do you seek information? He said: I ask you whether these trees bear fruit or not.

We said: Yes Thereupon he said: I think these would not bear fruits. He said: Inform me about the lake of Tabariyya? We said: Which aspect of it do you want to know? He said: Is there water in it? They said: There is abundance of water in it. Thereupon he said: I think it would soon become dry. He again said: Inform me about the spring of Zughar. They said: Which aspect of it you want to know? He (the chained person) said: Is there water in it and does it irrigate (the land)? We said to him: Yes, there is abundance of water in it and the inhabitants (of Medina) irrigate (land) with the help of it, He said: Inform me about the unlettered Prophet; what has he done? We said: He has come out from Mecca and has settled In Yathrib (Medina). He said: Do the Arabs fight against him? We said: Yes. He said: How did he deal with him? We informed him that he had overcome those in his neighbourhood and they had submitted themselves before him. Thereupon he said to us: Had it actually happened? We said: Yes. Thereupon he said: If it is so that is better for them that they should show obedience to him. I am going to tell you about. myself and I am Dajjal and would be soon permitted to get out and so I shall get out and travel in the land, and will not spare any town where I would not stay for forty nights except Mecca and Medina as these two (places) are prohibited (areas) for me and I would not make an attempt to enter any one of these two. An angel with a sword in his hand would confront me and would bar my way and there would be angels to guard every passage leading to it; then Allah’s Messenger (may peace be upon him) striking the pulpit with the help of the end of his staff said: This implies Taiba meaning Medina. Have I not, told you an account (of the Dajjal) like this? ‘The people said: Yes, and this account narrated by Tamim Dari was liked by me for it corroborates the account which I gave to you in regard to him (Dajjal) at Medina and Mecca. Behold he (Dajjal) is in the Syrian sea (Mediterranian) or the Yemen sea (Arabian sea). Nay, on the contrary, he As In the east, he is in the east, he is in the east, and he pointed with his hand towards the east. I (Fatima bint Qais) said: I preserved It In my mind (this narration from Allah’s Messenger (may peace be upon him).

When Tamim Dari told the Prophet (pbuh) of his encounter with the Dajjal on an island;

Sahih Muslim

041.7030 – Tamim Dari came to Allah’s Messenger (may peace be upon him) and informed Allah’s Messenger (may peace be upon him) that he sailed in an ocean and his ship lost direction and thus landed at an island. They moved about in that land in search of water. There they saw a person who had been pulling his hair. The rest of the hadith is the same. And he (Dajjal) said: If I were to be permitted to set out I would have covered all the lands except Taiba. Then Allah’s Messenger (may peace be upon him) brought (Tamim Dari) before the public and he narrated to them and said: That is Taiba and that is the Dajjal.

The warning to stay way away from Dajjal due to his confusing and convincing ways;

Sunan Abu Dawud

037.4305 – Narrated Imran ibn Husayn:

The Prophet (peace be upon him) said: Let him who hears of the Dajjal (Antichrist) go far from him for I swear by Allah that a man will come to him thinking he is a believer and follow him because of confused ideas roused in him by him.

Description about the Dajjal’s  physical appearance;

Sunan Abu Dawud

037.4306 – Narrated Ubadah ibn as-Samit:

The Prophet (peace be upon him) said: I have told you so much about the Dajjal (Antichrist) that I am afraid you may not understand. The Antichrist is short, hen-toed, woolly-haired, one-eyed, an eye-sightless, and neither protruding nor deep-seated. If you are confused about him, know that your Lord is not one-eyed.

Of the event where Tamim ad-Dari encountered the Dajjal on an island;

Sunan Abu Dawud

037.4311 – 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 one 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.