Tafsir of Yusuf 12:73

"They said: By Allah" (Tā-Allāhi). The majority of grammarians hold that the tā is a substitute for the wāw, just as it is substituted in turāth and tawrāh according to the Basrans. It is also said that it is a substitute for the bā'. Al-Suhayli said: It is a root unto itself. Al-Zajjaj said: One does not swear by it except in relation to Allah specifically; this is countered by the prohibition [of this view] due to its usage with al-Rabb (the Lord) absolutely or when possessed to the Ka‘bah, and with al-Rahmān, and [their] saying "by your greetings" (ta-hayyātika). Regardless, there is a sense of astonishment in swearing by it, as if they were astonished at being accused of what was mentioned, despite what was witnessed of their state. It has been narrated that they used to muzzle the mouths of their camels so they would not take anything from people's crops and food, and their reputation in Egypt for chastity, righteousness, and perseverance in various forms of obedience was well known.

Therefore they said: "You certainly know" (a knowledge that has reached the level of being certain and corresponding to reality) "that we did not come to cause corruption in the land." That is, to steal, for theft is among the greatest types of corruption; or to cause any corruption whatsoever in it, let alone what you have attributed to us regarding theft. The negation of coming for the sake of corruption, even if it does not necessitate, as the context requires, the negation of corruption absolutely, implies that they treated the arrival—which resulted in that [accusation], even by way of coincidence—as a coming with the intent of corruption. [This is] a maf‘ūl li-ajlihi (causal object) used rhetorically to demonstrate the complete heinousness of it in their view, and to foster the impossibility of its proceeding from them. It is as if they said: "If any corruption were to proceed from us, our coming would have been for that purpose," intending thereby to show the hideousness of such a state and to demonstrate their complete innocence from it. This is what has been said.

It is also said: They intended to negate that which is logically implied by coming for corruption in general—which is the very conception of corruption—as a hyperbole in their innocence of it. It is as if they said: "Corruption has never crossed our minds, nor has it occurred to our imagination, let alone its occurrence from us." Its remoteness is not hidden.

"And we have not been thieves." That is, we have never been characterized by theft at all. It is apparent that this is included within the scope of "you know," just as the first [clause was]. The reasoning for this is that knowledge of their witnessed states necessitates knowledge of their past states. The oath, in reality, is upon the two matters that are within the scope of knowledge, not upon the addressees' knowledge of that, except that they mentioned it for corroboration and emphasis of the speech. For this reason, the Arabs treated "knowledge" as equivalent to an oath, as in his saying:

And I have known that my death will surely come, For the arrows of fate do not miss their mark.

In this lies the compelling of the argument against them, and the verification of the astonishment understood from the tā' of the oath in their speech, as is contained within it. Some have mentioned that it is permissible for "that we did not come..." etc., to be the object of the knowledge, or for it to be the response to the oath, or the response to the knowledge because it contains its meaning; and it does not reject what has preceded.