O you who have believed...
This is a return to encouraging the believers and urging them to fight after having mentioned a portion of the scandals of their enemies.
"What is the matter with you"—an interrogation carrying the meaning of denunciation and rebuke.
"When it is said to you, 'March forth in the cause of Allah'"—that is, go out for Jihad. The root of al-nafr (marching forth), as it is said, is to depart for a matter that necessitates it.
"You cling heavily to the earth"—meaning you slowed down and did not hasten. Its root is tathaqaltum (you weighed yourselves down); Al-A'mash recited it as such, incorporating the ta into the tha and introducing a connective hamzah (alif al-wasl) to initiate speech with a quiescent letter. An example of this is the poet's saying:
She gives her bedfellow—if she desires him—modestly / A sweet flavor if she follows up the kisses.
With this, "when" (idha) is connected, and the sentence is in the position of a state (hal). The verb is past in form but present in meaning—that is, "What is the matter with you, clinging heavily, when the Messenger of Allah (may Allah bless him and grant him peace) said to you, 'March forth'?" It is permissible that the operational agent for "when" is the state of stability implied in "with you," or the meaning of the verb indicated by that—that is, "What thing has occurred or is occurring to you, or what are you doing when it is said to you, 'March forth'?"
It was recited as athaqaltum with a fathah on the hamzah, as an interrogative of denunciation and rebuke; the connective hamzah is dropped in pronunciation. According to this reading, it is not correct for "when" to be connected to this verb because an interrogation has the priority of position, and its governing object cannot precede it. Perhaps those who say that one may expand the scope of an adverbial phrase in a way not permitted elsewhere would allow this.
His saying, Exalted is He, "to the earth" is connected to "cling heavily" based on it implying the meaning of inclining and settling. Without this, it would not be connected with "to" (ila). That is: you clung heavily, inclining toward the world and its perishing desires, away from the [eternal] soon to come; and you disliked the hardships of Jihad and its troubles, which are followed by eternal rest and everlasting life. Or, it means inclining toward staying in your lands and homes. The first [interpretation] is more eloquent in its denunciation and rebuke, while the second is preferred as being further from the illusion of redundancy in the verse.
This sluggishness took place during the Expedition of Tabuk, which occurred in Rajab of the ninth year. For, after returning from Ta'if, the Prophet (may Allah bless him and grant him peace) stayed in Medina for a short time, then summoned the people to march forth during a time of hardship, intense heat, and drought in the land. The fruits of Medina had ripened and its shades were pleasant, despite the great distance and the large number of the enemy, making the departure difficult for them.
Ibn Hisham mentioned that the Messenger of Allah (may Allah bless him and grant him peace) rarely went out on an expedition without using an allusion, informing them that he intended a direction other than the one he was aiming for, except for the Expedition of Tabuk. The Prophet (may Allah bless him and grant him peace) clarified it to the people so that they might prepare for it accordingly.
"Are you satisfied with the worldly life" and its deception, "instead of the Hereafter?"—that is, in place of the Hereafter and its everlasting bliss.
"But the enjoyment of worldly life"—that is, its benefits and purposes, or the enjoyment of it and its pleasures—"in the Hereafter"—that is, compared to the Hereafter—"is but little"—despised and of no account. Using the noun instead of the pronoun here is for the sake of greater emphasis. This "in" is called the "comparative in," as the measured thing is placed alongside that which it is compared to. The embellishment of the worldly life with what suggests its value, while stripping the Hereafter of the like, is an exaggeration in demonstrating the baseness and vileness of the world and the greatness and exaltation of the Hereafter.
Ahmad, Muslim, Al-Tirmidhi, Al-Nasa'i, and others extracted from Al-Musawwir that he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "By Allah, the world in comparison to the Hereafter is only like one of you dipping his finger into the sea; let him see what he returns with."
Al-Hakim extracted—and authenticated—from Sahl that he said: The Messenger of Allah (may Allah bless him and grant him peace) passed by Dhu al-Hulayfah and saw a dead sheep with its leg sticking up. He said: "Do you see this sheep as insignificant to its owner?" They said: "Yes." He (upon him prayer and peace) said: "By the One in Whose hand is my soul, the world is more insignificant to Allah, the Exalted, than this is to its owner. If it were equal to the wing of a mosquito in the sight of Allah, He would not have given a disbeliever a drink of water from it."
I do not see the demonstration of the world's baseness as anything other than a demonstration made in a position of necessity. Indeed, it is the best of dwellings for one who takes provisions from it for his Hereafter.