Surah Yunus, Ayat 71

Ayat 71. And recite to them the news of Nuh (Noah). When he said to his people: "O my people, if my stay (with you), and my reminding (you) of the Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) of Allah is hard on you, then I put my trust in Allah. So devise your plot, you and your partners, and let not your plot be in doubt for you. Then pass your sentence on me and give me no respite. 

Hazrat Ibn Umar (May Allah be pleased with them) reported: We were talking about the Farewell Pilgrimage without knowing what was it when Messenger of Allah  [SAWW](PBUH) was also present. He (PBUH) stood up and recited the Praise and Glorification of Allah. He then gave a detailed account of Ad-Dajjal and said, 'Every Prophet sent by Allah had warned his people against his mischief. Nuh (PBUH) )warned his nation and so did all the Prophets after him. If he (i.e., Ad-Dajjal) appears among you, his condition will not remain hidden from you. Your Rubb is not one-eyed, but Ad-Dajjal is. His right eye is protruding like a swollen grape. Listen, Allah has made your blood, and your properties as inviolable as of this day of yours (i.e., the Day of Sacrifice), in this city of yours (i.e., Makkah), in this month of yours (i.e., Dhul -Hijjah). Listen, have I conveyed Allah's Message to you?'' The people replied in affirmative. There upon he said, "O Allah, bear witness.'' And he repeated it thrice. He (PBUH) concluded: "Do not revert after me as infidels killing one another". [Al-Bukhari Volume 4, Book 55, Number 553].  

Lesson : as mentioned above in Surah Yunus Ayat 71. "And recite to them the news of Nuh (Noah). When he said to his people:"

This Hadith brings out the following three points:

1. Some marks and signs of pseudo-Messiah (Al-Masih Ad-Dajjal) are mentioned to warn the believers against his mischief.

2. The lives and properties of Muslims are inviolable for each other. In other words, it means that each of them is a protector and guardian of the life, property and honour of the other.

3. Internal war among the Muslims is a great crime and can even lead to infidelity (Kufr). May Allah save us all from it.