Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(If ye help him not) if you do not help Muhammad (pbuh) by going forth with him to the battle of Tabuk, (still Allah helped him when those who disbelieve) the disbelievers of Mecca (drove him forth, the second of two) i.e. the Messenger of Allah and Abu Bakr; (when they two) Allah's Messenger (pbuh) and Abu Bakr, may Allah be well pleased with him, (were in the cave, when he) the Prophet (pbuh) (said unto his comrade) Abu Bakr: (Grieve not) O Abu Bakr. (Lo! Allah is with us) and He will help us. (Then Allah caused His peace of reassurance) His tranquillity (to descend upon him) upon His Prophet (and supported him) helped him on the Day of Badr, at the battle of the troops and also on the Day of Hunayn (with hosts ye cannot see) i.e. with angels, (and made the word) the religion (of those who disbelieved the nethermost) blameworthy and defeated, (while Allah's word it was that became the uppermost) triumphant and praiseworthy. (Allah is Mighty) in retribution against his enemies, (Wise) in helping His friends.
If you do not help him, that is, the Prophet (s), [know that] God has already helped him, when the disbelievers drove him forth, from Mecca, that is, they made him resort to leaving, when they desired to kill him or imprison him or banish him at the council assembly — the second of two (thāniya ithnayn: this is a circumstantial qualifier), that is, one of two, the other being Abū Bakr: in other words, just as God helped him in such a situation, He will not forsake him in another; when (idh substitutes for the previous idh) the two were in the cave — a breach in the mountain called Thawr — when (idh substituting again), he said to his companion, Abū Bakr — who, upon perceiving the [sound of the] feet of the idolaters [nearby], had said to him, ‘If one of them should merely look below his feet, he will definitely see us!’ — ‘Do not despair; verily God is with us’, assisting [us]. Then God sent down His Spirit of Peace upon him, His reassurance — some say this means upon the Prophet, others, that it means upon Abū Bakr — and supported him, that is, the Prophet (s), with legions, of angels, you did not see, [both] in the cave and in the locations in which he fought battles; and He made the word of those who disbelieved, that is, the call to idolatry, the nethermost, the one vanquished, and the Word of God, that is, the profession of His Oneness (shahāda), was the uppermost, the one prevailing and triumphant. And God is Mighty, in His Kingdom, Wise, in His actions.
(when the disbelievers drove him out, the second of the two;) During the year of the Hijrah, the idolators tried to kill, imprison or expel the Prophet, who escaped with his friend and Companion, Abu Bakr bin Abi Quhafah, to the cave of Thawr. They remained in the cave for three days so that the pagans who were sent in their pursuit, returned (to Makkah), and they proceed to Al-Madinah. While in the cave, Abu Bakr was afraid the pagans might discover them for fear that some harm might touch the Messenger. The Prophet kept reassuring him and strengthening his resolve, saying,
(O Abu Bakr! What do you think about two, with Allah as their third) Imam Ahmad recorded from Anas that Abu Bakr said to him, "I said to the Prophet when we were in the cave, `If any of them looks down at his feet, he will see us.' He said,
(and made the word of those who disbelieved the lowermost, while the Word of Allah that became the uppermost;) Ibn `Abbas commented, "'The word of those who disbelieved', is Shirk, while, `The Word of Allah' is `La ilaha illallah.'' It is recorded in the Two Sahihs that Abu Musa Al-Ash`ari said, "The Messenger of Allah was asked about a man who fights because of courage, or out of rage for his honor, or to show off. Whom among them is in the cause of Allah' The Prophet said,
(He who fights so that Allah's Word is superior, then he fights in Allah's cause.)'' Allah said next,
(and Allah is All-Mighty), in His revenge and taking retribution, He is the Most Formidable and those who seek refuge with Him and take shelter by adhering to what He instructs are never made to suffer injustice,
(All-Wise), in His statements and actions.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
From here begins the discourse (vv. 38-72) which was sent down at the time when the Holy Prophet was engaged in making preparations for the Campaign to Tabuk.
".... you should know that the goods... Hereafter" may imply two meanings. First: "When you will find that the life in the Hereafter is eternal and see that the good things and the provisions of enjoyment are countless, you will realize that the potential and the actual enjoyments of the temporary life of this world were nothing as compared with the blessings of that great Kingdom. At that time you will regret why you deprived yourselves of this everlasting happiness and bliss for the sake of the little-very little-sort-lived enjoyments of the mortal life of this world. " Second: "The goods of this worldly life are of no value in the Hereafter, howsoever abundant they might be. You shall have to give up each and everything as soon as you breathe your last, for nothing of this world can go with you to the Next World. Of course, you will get credit for what you sacrificed for the pleasure and love of Allah, and love of Islam."
A general rule of the Islamic conduct has been derived from "If you.... chastisement. " When the Muslims are commanded to go to Jihad by a public proclamation from their leader, it becomes an obligatory duty for those who are called upon to do Jihad, whether they belong to any particular group or region. So much so that the Faith of those who do not go for Jihad without a genuine excuse becomes doubtful. But even in cases where the Muslims are called upon to go forth for Jihad and there is no command for the compulsory enrollment of every able-bodied Muslim of a particular group or region, it is a religious duty (though not obligatory), and it shall be considered to have been performed even if only some Muslims go forth for it.
That is, "Allah's work does not depend on you and will be accomplished only if you do it. It is Allah's grace and bounty that He is affording you the golden opportunity of serving the cause of His Way. Therefore if you miss this opportunity because of any foolish assumption, Allah will raise another people and bestow on them the opportunity and capability of doing His work, and you will be losers".
This refers to the occasion when the disbelievers had decided to assassinate the Holy Prophet, and the very night fixed for his assassination he had left Makkah for Al-Madinah. By that time most of the Muslims had migrated to Al-Madinah in twos and threes and only a few helpless ones had remained behind in Makkah. As he was sure that he would be pursued, he took only Hadrat Abu Bakr with him and went southward instead of following the northern route to Al-Madinah and remained hidden in the Thaur Cave for three days. In the meantime the blood thirsty enemies had begun to make a thorough search for him all around Makkah and some of them reached the very mouth of the Cave where he was hidden. On this critical occasion Hadrat Abu Bakr naturally felt alarmed lest they should peep into the Cave, and see them. But the Holy Prophet remained as calm as before and reassured his Companion, saying, "Be not distressed: indeed Allah is with us."
The words ".... whether you are light or heavy..." have a very comprehensive meaning: "When it is enjoined to march forth for Jihad, you must go forth anyhow, whether you like it or not: whether you are in a state of prosperity or indigence: whether you are well-equipped or ill-equipped: whether the circumstances are favorable or adverse: whether you are young and healthy or old and weak. "