Masruq narrates: I was sitting with Sayyiduna Abdullah (may Allah be pleased with him). He was lying down among us when a man came to him and said: Near the gates of Kindah, a preacher was delivering a sermon and saying that the sign of the smoke (which is mentioned in the Qur'an) will soon come and will seize the breaths of the disbelievers, and the believers will feel something like a cold due to it. So Sayyiduna Abdullah (may Allah be pleased with him) sat up angrily. He said: O people, fear Allah! Whoever among you knows something, let him speak according to it, and whoever does not know, let him say: Allah knows best. For the greatest scholar among you is the one who, regarding something he does not know, says: Allah knows best. Allah Almighty said to His Prophet: "Say: I do not ask you for any reward for this, nor am I of those who invent." (Sayyiduna Abdullah, may Allah be pleased with him, explained:) When the Prophet (peace and blessings be upon him) saw the people turning away (from accepting Islam), he prayed: "O Allah! Send upon them a famine like that in the time of Yusuf (peace be upon him)." So famine seized them until they began to eat carrion and skins. If any one of them looked towards the sky, he would see smoke. Abu Sufyan came to the Prophet (peace and blessings be upon him) and said: O Muhammad (peace and blessings be upon him), you have come to command obedience to Allah and to enjoin the ties of kinship, while your people are perishing due to hunger. Pray to Allah for them. Upon this, Allah Almighty revealed this verse: "Then watch for the Day when the sky will bring a visible smoke." (And in another place, Allah Almighty says:) "On the Day We will strike with the greatest assault, indeed, We will take retribution." So here, the assault refers to the occasion of the Battle of Badr, while the signs of the smoke, the assault, the blame, and the people of Rome have already passed.