Bukhari

Hadith Commentary:
These are the fifth signs related to the signs of the Hour (Day of Judgment).

The smoke is the same as mentioned in: ﴿ يَوْمَ تَأْتِي السَّمَاءُ بِدُخَانٍ مُبِينٍ ﴾ ().

The splitting of the moon is the same as mentioned in Surah: ﴿ اقتربتِ الساعةُ وانشقَ القَمرُ ﴾ ().

From this statement of Abdullah ibn Mas'ud radi Allahu anhu, it is clearly understood that the splitting of the moon was a sign of the Hour, but since the Prophet sallallahu alayhi wa sallam had foretold it beforehand, in that respect it was also a miracle.

Shah Waliullah rahimahullah has written similarly in "Tafhimat".

Thirdly, the Romans, who were very proud of their power, being defeated at the hands of the Persians.

"Batshah" (seizure) is mentioned in the verse: ﴿ يَومَ نَبطِشُ البطشةَ الکُبریٰ ﴾ (), and in the verse: ﴿ فسوفَ یَکُونُ لِزَاما ﴾ (), "laziman" (inevitability) means that this destruction was certain to occur.

This refers to the destruction that befell the disbelievers on the Day of Badr.

By "Batshah" as well, the killing of the disbelievers is meant, which occurred on the Day of Badr.

Some have said that by "laziman" the Day of Judgment is meant.

Some have said that it refers to the famine that came upon the Quraysh of Makkah as a punishment.

Hadith Commentary:
1.
By "smoke" is meant the verse of Surah ad-Dukhan:
“When the sky will bring forth manifest smoke.”
As for the splitting of the moon, it refers to:
“The Hour has drawn near, and the moon has split.”
(al-Qamar: 1)
The mention of Rome is in Surah ar-Rum:
“Alif Lam Meem. The Romans have been defeated.”
(ar-Rum: 1,2)
The mention of (batshah) is in ad-Dukhan:
“The Day We will seize with the greatest seizure.”
(ad-Dukhan: 16)
By (lizam) is meant the verse that has been mentioned above.

Abdullah ibn Mas‘ud radi Allahu anhu used to say that all five of these signs of the Hour have already occurred.
He used to say that by “smoke” is meant that smoke which the Quraysh of Makkah saw in the sky due to the severity of hunger.
The miracle of the splitting of the moon (shaqq al-qamar) also occurred before the Hijrah.
The manifestation of “The Romans have been defeated” (ghulibat ar-Rum) has also already taken place.
All the commentators are agreed upon this, and by (batshah) is meant that severe seizure which appeared in the form of the killing of the disbelievers of Quraysh on the Day of Badr, and by lizam is meant the capture and imprisonment of the disbelievers in the Battle of Badr.

Whereas, according to the majority of the scholars, (batshah) refers to the seizing of the disbelievers and casting them into Hell, and since the disbelievers of Makkah denied Allah and His Messenger sallallahu alayhi wa sallam, they must necessarily suffer its punishment: in this world, in the form of defeat at the Battle of Badr, and in the Hereafter, by being subjected to the eternal punishment of Hell.

And Allah knows best.