Tafsir of As-Saff 61:11

(You believe in Allah and His Messenger and strive in the cause of Allah with your wealth and your lives)

This is an explanatory resumption [of the preceding discourse], as if it had been asked: "What is this trade? Direct us to it." Thus, it was said: "You believe," etc. The imperfect tense in both instances—as stated by al-Mubarrad and a group [of scholars]—is an indicative verb serving the meaning of an imperative; that is, "Believe and strive." This is supported by the reading of ‘Abdullah [ibn Mas‘ud] in the imperative form. Using the imperfect tense [in the Qur’anic text] is intended to intimate the necessity of compliance, as if [the acts of] belief and jihad had already occurred, and [Allah] is informing [them] of their occurrence.

If the address is directed to the sincere believers, the intention is: "You shall persist and remain steadfast in faith," or "You shall combine faith and jihad"—that is, combine the perfection of the self [through faith] with the perfection of others [through striving]. If it is addressed to those who are believers in appearance only, the intention is: "You shall make your faith sincere." In either case, there is no difficulty regarding the command.

Al-Akhfash said: "You believe," etc., is an explicative clause (‘atf bayan) for "trade." This was countered by the claim that this is only conceivable on the assumption that the original structure was an tu’minu (that you believe), so that it could be interpreted as an infinitive (masdar), then the an was omitted, causing the verb to be in the nominative case—as in his [the poet's] saying: "Do not, O you who chide me [for] attending the war"—meaning an ahdura (that I attend). When the an was omitted, the verb became nominative; however, this is rare.

Ibn ‘Atiyyah said: "You believe" is a verb in the nominative case based on the estimation [of an elided subject], "That is, you believe." This involves the omission of the subject (mubtada’) and [the particle] anna with its noun, while retaining its predicate. Regarding this, Abu Hayyan stated: This is not permissible.

Zayd ibn ‘Ali read [the verse as] tu’minu wa tujahidu (with the omission of the nun of the nominative case in both), based on the implied lam of command; that is, "Let you believe and strive," or "Let you strive," as in his [the poet's] saying: "I said to a doorkeeper at her gate: 'Grant us leave; for I am one of her protectors,'" and similarly his saying: "Muhammad, may every soul be a ransom for your soul, when you fear an affair that will destroy you."

Others permitted it to be an independent sentence (isti’naf), with the nun being omitted for lightness, as in the reading [of the Quran]: "Two sorcerers supporting each other," and his [the poet's] saying: "And we graze whatever you wish to be grazed; you have raised the pride, so what are you warning against?" and likewise his saying: "You sleep, I traverse by night, and you spend the night rubbing your face with ambergris and fragrant musk." You know that this omission [of the nun] is anomalous (shadhdh).

(That is best for you)—meaning what has been mentioned of belief and jihad—(if you only knew)

(11) (That is, if you are among the people of knowledge, for the actions of the ignorant are not considered until they are described as 'best.') It is also said: Its meaning is, "If you knew that it is best for you, it would be best for you at that time." This is because when you know that and believe it, you will love faith and jihad more than you love your wealth and your lives; thus, you will be sincere and will prosper.