What or who is the Dajjal?

Question:

What or who is the Dajjal?

Answer:

In the Name of Allah, the Merciful, Compassionate
May His peace and blessings be upon His messenger Muhammad, his family, folk, companions, and those who follow him until the end of time.
Dajjal is a person whom the Prophet (may the peace and blessings of Allah be upon him) described as appearing at the end of time. He is sent by Allah as a trial to people. Dajjal will claim godhood and Allah will allow supernatural acts to occur at his hands, such as bringing back to life those he kills, causing the sky to rain by his command, and the earth to produce vegetation by his command. He will have with him what resembles Paradise and Hell. The one he claims is Paradise is in reality Hell, and the one he claims is Hell is in reality Paradise. He will also have two rivers flowing with him. All of these things will be made to happen for him by the Power and Will of Allah. Whoever follows him will disbelieve and be misfortunate and remorseful. Whoever disbelieves him is the true Believer whom Allah has granted success to be of the felicitous. May Allah make us of those who are granted the success of felicity.
Of the signs of Dajjal is that he is one-eyed, and he will have the letters ك ف ر (k f r : the arabic root letters for disbelief) between his eyes. Every Believer, even if illiterate, will be able to read and recognize the letters. All of these descriptions are found in rigorously authenticated reports from al-Bukhari, Muslim, and others.
Then Allah will make him incapable of these supernatural events, so that he is not able to kill anyone, and his command is no longer executed. Then Prophet Jesus (upon him be peace) will kill him.
Because of the enormity of the trial that Dajjal will put people through, the Prophet (upon him be Allah's peace and blessings) encouraged us to seek refuge in Allah after every prayer from the tribulation of Dajjal. Bukhari and Muslim relate the hadith from Abu Hurayra (may Allah be pleased with him) that the Prophet said, "After one of you finishes his tashahhud (what is read in the sitting of the prayer [i.e. after he finishes his prayer]) let him seek refuge in Allah from four things: the fire, the torment of the grave, the trials of life and death, and the trial of the Imposter Messiah, the Dajjal.
Bukhari and Muslim also relate from Abu al-Darda' (may Allah be pleased with him) that the Prophet (may Allah send His peace and blessings upon him) said, "Whoever memorizes the first ten verses of Surat al-Kahf shall be protected from Dajjal," and in another version of the hadith he mentioned the last ten verses. Imam al-Nawawi says in Sharh Muslim, "It is said the reason for this [i.e. benefit of memorizing the mentioned verses of al-Kahf] is that its beginning contains wondrous events and signs. He who reflects on their meaning will not suffer the trial of Dajjal. Its final verses, beginning from, 'Do those who disbelieve...,' are similar [in what they contain]."
Al-Nawawi mentions the words of the prominent Imam al-Qadi `Iyad al-Maliki from his The Tenets of Faith of Ahl al-Sunnah, "These hadith which Muslim and others relate regarding the story of Dajjal are a proof of his reality for the way of those of truth. He is a particular person whom Allah sends as a trial to His slaves. Allah gives him the power to do things, and they are only from His powers... This is the way of Ahl al-Sunnah, the Scholars of Hadith and Jurisprudence, and their like."
This is a brief account about Dajjal. He who wants further information should look in Sahih al-Bukhari and Sahih Muslim along with their commentaries.