Tafsir of Yusuf 12:104

"And you do not ask them for it" — meaning this news, or its kind, or the Qur’an; regardless of what it is, the pronoun refers to what is understood from what preceded it. The meaning is: You do not demand from them, for conveying it, "any reward"—that is, any compensation, as the bearers of news do.

"It is nothing but a reminder"—that is, it is nothing but a recollection and a sermon from Allah, the Exalted, "for the worlds," all of them. The sentence acts as a justification for what preceded it, because a general sermon is inconsistent with taking a fee from some, as it is not exclusive to them.

It has been said: It is intended that it is nothing but a sermon from Allah, the Glorified, which I have been commanded to convey, and therefore it is an obligation. How then could I ask for a reward for performing an obligation? However, this is contrary to the apparent meaning. Based on that interpretation, the verse would be evidence for the prohibition of taking a fee for performing obligatory duties.

Mubashir ibn Ubayd read it as "And we do not ask them" (using the nun).