What is the legal ruling for someone who returns to distorting the words of the Qur’an with obscene language after showing repentance, and was what we did, first concealing his act and then reporting him, correct from a Sharia perspective?

Writing obscene words on the Mus'haf (Quran) is a reprehensible crime, an act of disbelief (kufr), and apostasy (riddah). It is among the actions of sorcerers to invoke devils. The book "Shams al-Ma'arif al-Kubra" is a book of sorcery and misguidance; it is not permissible to read it. The best course of action is to burn both books and cover up for the perpetrator, hoping for his repentance, and to inform the competent authorities if he returns to his misguidance.

Whoever is proven to be involved in sorcery or to have mocked the Mus'haf is to be asked to repent. If he repents, all is well; otherwise, he is to be executed. Malik and Ahmad were of the opinion that the sorcerer is to be executed without being asked to repent, due to the actions of the Companions and because the knowledge of sorcery does not vanish with repentance. The execution of a sorcerer has been authentically reported from Umar, Hafsa, and Jundub. Imam al-Bukhari narrated that Umar (may Allah be pleased with him) wrote to them: "Kill every sorcerer and sorceress."