Masruq (may Allah have mercy on him) says that once, in the main mosque, a man was saying that on the Day of Resurrection, a smoke will descend from the sky, it will take away the eyes and ears of the hypocrites, and it will enter the breaths of the Muslims causing a condition like cold. I went to Sayyiduna Ibn Mas'ud (may Allah be pleased with him) and told him this. He was sitting reclining, but upon hearing this, he sat up straight and said: O people! Whoever knows something well can speak about it, and whoever does not know something well should say that Allah knows best, because it is also a sign of a person's wisdom that he says "Allah knows best" about what he does not know. The revelation of the mentioned verse happened in this context: when the Quraysh exceeded all limits in disobeying the Prophet (peace be upon him), the Prophet (peace be upon him) prayed for a famine upon them like that in the time of Yusuf (peace be upon him). So, the Quraysh were surrounded by famine and difficulties, to the extent that they were forced to eat bones, and the situation became such that when anyone looked towards the sky, due to hunger, he would see smoke between himself and the sky. Upon this, Allah revealed this verse: «‏‏‏‏﴿فَارْتَقِبْ يَوْمَ تَأْتِي السَّمَاءُ بِدُخَانٍ مُبِينٍ o يَغْشَى النَّاسَ هَذَا عَذَابٌ أَلِيمٌ﴾» ‏‏‏‏ [الدخان: 10-11] "Wait for the Day when a clear smoke will come from the sky, which will envelop the people; this is a painful punishment." After this, some people came to the Prophet (peace be upon him) and said, "O Messenger of Allah (peace be upon him)! Pray for rain for Banu Mudar, they are perishing." So the Prophet (peace be upon him) prayed for them, and this verse was revealed: «‏‏‏‏﴿إِنَّا كَاشِفُو الْعَذَابِ قَلِيلًا﴾» ‏‏‏‏ [الدخان: 15] "We are removing the punishment from them." But when, after receiving prosperity, they returned to their previous actions, this verse was revealed: «‏‏‏‏﴿يَوْمَ نَبْطِشُ الْبَطْشَةَ الْكُبْرَى إِنَّا مُنْتَقِمُونَ﴾» ‏‏‏‏ [الدخان: 16] "On the Day We will seize them with a mighty grip, We will indeed take retribution." And this refers to the Battle of Badr. If it had been the Day of Resurrection, Allah would not have removed that punishment from them.