Based on these divisions, let us try to gauge to which Age group the Messenger Nooh (a.s.) (Noah) belonged. We find from the Qur'an that Nooh (a.s.) remained among his nation for 950 years.
Allah has used the word 'nakesh' to describe his stay among his people, however, it is not clear from this statement if Nooh (a.s.) preached futilely among his nation for 950 years, or if he lived a total of the 950 years. However, the former might have been the case, since he could not have attained prophet-hood till he was mature of age, supposing that took somewhere between four to five hundred years, after which he preached to his people for another 950 years. Therefore, it would be correct to assume that he was 1400 or 1500 years old at the time of the Great Deluge and he remained among his people for sometime after the Flood as well, so Nooh (a.s.) lived for roughly two thousand years. On the other hand, if we take that he was 950 years old when the Flood struck, and the time he spent among his handful disciples following it to be 300, 400 or even 500 years, we reach about 1500 years. The highest life expectancy among the people of the Dapar Age was two thousand years, so I conclude Nooh (a.s.) to have lived during that era.
Now let us try to understand why the warning of Dajjal's coming commenced from the time of Nooh (a.s.) and not earlier. I can think of no better reason than the fact that a falsehood of Dajjal's magnitude could neither emerge nor sustain during the periods of absolute truth as were prevalent in the Ages of Sattya (Truth) and Treta., when truth would prevail 100 and 50 times respectively over falsehood, therefore there was no potentiality of it taking place during those times. Dajjal is known to us as the attractive impostor, a liar, a deceiver-described as such in the Hadis and the Bible as Anti-Christ. The possibility of Dajjal's birth rose in the era of Dapar, Nooh's time, when truth succumbed to falsehood 50 times out of hundred. Although Dajjal was destined to emerge a lot later in time, in the Koli Yug, the Later Age, the potentiality rose substantially in its favor and hence the commencement of the warnings.
In all probability, and this is what the Messenger of Allah sought to explain using different allegories, that of Dajjal being kept prisoner in a faraway island might refer to the low potentiality of it emerging during the first two phases of mankind's existence. Despite the fact of Dajjal being the most important event in the history of the world, warnings about it started only from the time of Nooh (a.s.). This goes to stress that a liar or deceiver of Dajjal's enormity could not express itself or bring the whole world within its grasp during the eras of Truth and Treta.
At this point, there's one thing worth mentioning. There is a section of people who stress great importance on the issue of Abu Sayyad (ra); so much so that an entire chapter in the Meshkat has been devoted to the depiction of his life and different opinions about him. It so happened that a baby quite unusual or different, was born into a Jewish family in Madina. There are reports of the Messenger of Allah having gone to see him, but there is no basis for speculating that baby as being the Dajjal, for the Messenger of Allah neither said anything to that effect nor let it be known that he thought this baby to be the personification of the Dajjal. The Messenger of Allah was the one to inform the world of the coming of the Dajjal during the time of Isa's (a.s.) (Jesus) return to earth and the Mahdi's Emamate and that it would be destroyed by Isa (a.s.) himself. How then could this Kafer appear within the holy presence of the Messenger of Allah himself, that too, in the city of Madina itself? Besides that, the Messenger of Allah had already predicted the inability of the Dajjal to enter either Makkah or Madina,
whereas Ebne Sayyed was born in Madina itself and performed Hajj in Makkah. The misnomer of Dajjal, Ebne Sayyed had converted to Islam, whereas the Dajjal is to die a Kafer.
He himself refuted people's talk of him being the Dajjal pointing to the fact that he had children; in accordance to the Hadis of the Messenger of Allah, the Dajjal will have no children. Ebne Sayyed died a natural death and the Dajjal is destined to be destroyed by Isa (a.s.).
Apostates and cruel rulers have also, in cases been termed as Dajjals or deceivers and liars by the Messenger of Allah, but they are far removed from the actual and the particular Dajjal whom he and other Messengers have warned about.
Abu Sayyad (ra) has been mistakenly singled out as the Dajjal of the later times and a whole chapter in the Meshkat has been devoted in trying to prove him as the one. However, since I have been correctly able to ascertain Dajjal's identity through the blessings of Allah and His Messenger, I do not attach any importance to the details regarding Abu Sayyad (ra). That most people have been unable to grasp the allegorical references to the Dajjal is further proved by their insistence in trying to establish Abu Sayyad as the self-same Masih al Kazzab.
The Qur'an- Sura Ankabut-14.
Hadis, Bokhari and Muslim.
Hadis, Muslim from Abu Sayeed Khudri (Ra).