Tafsir of Ta-Ha 20:104

"We are best knowing of what they say"—that is, of that which they say, which is the duration of their stay—"when the most exemplary of them in way says"—that is, the most just of them in opinion and the soundest of them in intellect. And "when" is an adverbial modifier for "they say": "You have not tarried but one day."

It is said that the intended meaning of "day" is absolute time, and its being indefinite is for the sake of minimization and belittlement; thus, the meaning is: "but a little while." However, the obviousness of the contrast with [the mention of] ten [days in other verses] makes this unlikely. Attributing this statement to the "most exemplary of them" is an endorsement by the Exalted of his [intellectual] priority, yet not because it is closer to the truth, but because it is more profound in expressing regret, or because it is more indicative of the intensity of the horror. This proves that the speaker of this statement is more aware of the atrocity of the matter and the severity of the torment.