Is it true what is narrated about a group of Muslims who met a man who asked them about the time and the advent of Prophet Muhammad (peace and blessings be upon him), then said that this was not the time for his emergence, and it was said that he was the Dajjal?

The story mentioned is the Hadith of Al-Jassasah, a great hadith narrated by Muslim. The Prophet, peace and blessings be upon him, gathered his companions to tell them the story of Tamim al-Dari, a Christian who embraced Islam. His account corroborated what the Prophet had said about the Antichrist (Al-Masih Ad-Dajjal).

The story of Tamim is that he embarked on a sea journey with thirty men, and the waves tossed them for a month until they reached an island. There, they were met by a hairy beast called Al-Jassasah, which directed them to a man in a monastery. When they entered the monastery, they found a man bound in shackles, and he was the Dajjal.

The Dajjal asked them about the date palms of Baysan, the Sea of Galilee (Lake Tiberias), and the spring of Zughar, and whether its water was used by its people for cultivation. He informed them that all of them were on the verge of drying up. Then he asked them about the Prophet of the unlettered people and what he had done. They told him that he had emerged from Mecca, settled in Medina, and prevailed over the Arabs, who had obeyed him. He then said to them: "Indeed, I am the Messiah, and I am about to be granted permission to emerge. I will emerge and travel through the earth, leaving no town but that I will enter it within forty nights, except Mecca and Taybah (Medina)."

The Prophet, peace and blessings be upon him, pointed towards the East and confirmed that Tamim's account agreed with what he had been telling them about the Dajjal, Mecca, and Medina.