In the 1st / 7th century Jerusalem and the Holy Land came under Muslim sovereignty. To Muslims also the two places were sacred, and in the centuries to come, despite often troubled times politically, adherents of all three faiths continued to undertake pilgrimages to the Holy Sites in the area many of which were revered by all three religions. Successive Muslim rulers, Caliph 'Umar ibn al-Khattab (r. AH 13–23 / AD 634–44) and Salah al-Din al-Ayyubi (Saladin, r. 564–89 / 1169–93) most famous among them, devoted themselves to protecting the pilgrimage routes, providing generously for the upkeep of the holy sites and facilitating access for all – Muslims and non-Muslims alike – a sacred duty imparted by the Qur'an itself, which respects Jews and Christians as 'People of the Book' ('ahl al-kitab').