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]. (JA)
App reference (JA): Book 18, Hadith 284 (JA)
Arabic/English book reference (JA): Book 18, Hadith 1794 (JA)