Ibn 'Umar (May Allah be pleased with them) said:
The Messenger of Allah (ﷺ) forbade travelling to the land of the enemy carrying the Qur'an.[Al-Bukhari and Muslim]. (DE)
App reference (DE): Book 18, Hadith 284 (DE)
Arabic/English book reference (DE): Book 18, Hadith 1794 (DE)