Sunan Ibn Majah, Book 24, Hadith 2990 (In-Book) ⓘ
It was narrated from Ibn ‘Umar that the Messenger of Allah used to forbid traveling with the Qur’an to the land of the enemy, lest the enemy gets hold of it.
حَدَّثَنَا مُحَمَّدُ بْنُ رُمْحٍ، أَنْبَأَنَا اللَّيْثُ بْنُ سَعْدٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم أَنَّهُ كَانَ يَنْهَى أَنْ يُسَافَرَ بِالْقُرْآنِ إِلَى أَرْضِ الْعَدُوِّ مَخَافَةَ أَنْ يَنَالَهُ الْعَدُوُّ .
also referenced under: Hadith 2880 (Reference) & Volume 4, Book 24, Hadith 2880 (DarusSalam)