Is one who unintentionally steps on a page from the Qur'an, because it was lying on the ground, sinful? Is expiation incumbent upon him for that? And is this act considered disbelief?

One must beware of mocking the verses of Allah and the hadiths of His Messenger. This includes turning the pages of the Mushaf with saliva, or throwing papers containing the name of Allah and His Messenger into the trash, or leaving them in the street. Whoever does this intentionally, knowing what is on the paper, commits an act of disbelief (kufr). Whoever does it out of ignorance commits a sin, due to the possibility of a verse or hadith being present. Allah Almighty says: "And whoever honors the sacred rites of Allah – it is better for him in the sight of his Lord" and "And whoever honors the symbols of Allah – indeed, it is from the piety of hearts." Allah Almighty says: "Say, 'Is it Allah and His verses and His Messenger that you were mocking?' Make no excuse; you have disbelieved after your belief." As for one who falls into this unintentionally, he does not commit kufr, but he sins if he is negligent, and repentance is obligatory upon him. One who is not negligent and this happens to him due to forgetfulness bears no blame, for Allah Almighty says: "Our Lord, do not impose blame upon us if we forget or make a mistake," and the Prophet, peace and blessings be upon him, said: "Indeed, Allah has pardoned for my Ummah mistakes, forgetfulness, and what they are coerced into."