What is the ruling on one who swore by the Qur’an not to do something, and appended to the oath that Allah would not admit him to Paradise if he broke it, and does the condition take effect if he breaks it intentionally or inadvertently, and what is the expiation for this oath?

Whoever swears by the Mus'haf (copy of the Qur'an) and then breaks their oath must offer an expiation for an oath, because what is in the Mus'haf is the Word of Allah, and His Word is one of His attributes. An oath is valid when made by it, just as it is valid when made by His Names.

The expiation for an oath is to feed ten needy persons with an average of what one feeds their own family, or to clothe them, or to free a slave.

If one cannot find any of these, then they must fast for three days, based on the saying of Allah the Almighty: "Its expiation is the feeding of ten needy people from the average of that which you feed your [own] families or clothing them or freeing a slave. But whoever finds not [the means to do so] - then a fast of three days. That is the expiation for oaths when you have sworn. But guard your oaths." (Al-Ma'idah: 89).

It is not appropriate to emphasize or magnify the oath with what was mentioned about not entering Paradise or similar statements.

If the breaking of the oath was due to forgetfulness, there is no sin upon him, but if it was intentional, then his matter is with Allah the Almighty.