The prohibition of travelling with the Mushaf to the land of the disbelievers if there is the fear that it may fall into their hands. Sahih Muslim 1869 a
Arabic hadith text
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ،
قَالَ نَهَى رَسُولُ اللَّهِ صلى الله عليه وسلم أَنْيُسَافَرَ بِالْقُرْآنِ إِلَى أَرْضِ الْعَدُوِّ .
Translation
It has been narrated on the authority of Ibn 'Umar who said
The Messenger of Allah (ﷺ) forbade that one should travel to the land of the enemy taking the Qur'an with him.