Genghis Khan was a Tengrist, but was religiously tolerant and interested in learning philosophical and moral lessons from other religions. He consulted Buddhist monks (including the Zen monk Haiyun), Muslims, Christianmissionaries, and the Taoist monk Qiu Chuji.
According to the Fozu Lidai Tongzai written by Nian Chang (b. 1282) Genghis Khan’s viceroy Muqali was pacifying Shanxi in 1219, the homeland of Zen Buddhist monk Haiyun (海雲, 1203-1257), when one of Muqali’s Chinese generals, impressed with Haiyun and his master Zhongguan’s demeanor, recommended them to Muqali. Muqali then reported on the two to Genghis Khan who issued the following decree on their behalf: “They truly are men who pray to Heaven. I should like to support them with clothes and food and make them chiefs. I’m planning on gathering many of this kind of people. While praying to Heaven, they should not have difficulties imposed on them. To forbid any mistreatment, they will be authorized to act as darqan (possessor of immunity).” Genghis Khan had already met Haiyun in 1214 and been impressed by his reply refusing to grow his hair in the Mongol hairstyle and allowed him to keep his head shaven. After the death of his master Zhongguan in 1220, Haiyun became the head of the Chan (Chinese Zen) school during Genghis Khan’s rule and was repeatedly recognized as the chief monk in Chinese Buddhism by subsequent Khans until 1257 when he was succeeded as chief monk by another Chan master Xueting Fuyu the Mongol-appointed abbot of Shaolin monastery.
Genghis Khan summoned and met the Daoist master Qiu Chuji (1148-1227) in Afghanistan in 1222. He thanked Qiu Chuji for accepting his invitation and asked if Qiu Chuji had brought the medicine of immortality with him. Qiu Chuji said there was no such thing as a medicine of immortality but that life can be extended through abstinence. Genghis Khan appreciated his honest reply and asked Qiu Chuji who it is that calls him eternal heavenly man, he himself or others. After Qiu Chuji replied that others call him by that name Genghis Khan decreed that from thenceforth Qiu Chuji should be called “Immortal” and appointed him master of all monks in China, noting that heaven had sent Qiu Chuji to him. Qiu Chuji died in Beijing the same year as Genghis Khan and his shrine became the White Cloud Temple. Following Khans continued appointing Daoist masters of the Quanzhen School at White Cloud Temple. The Daoists lost their privilege in 1258 after the Great Debate organized by Genghis Khan’s grandson Mongke Khan when Chinese Buddhists (led by the Mongol-appointed abbot or shaolim zhanglao of Shaolin monastery), Confucians and Tibetan Buddhists allied against the Daoists. Kublai Khan was appointed to preside over this debate (in Shangdu/Xanadu, the third meeting after two debates in Karakorum in 1255 and 1256) in which 700 dignitaries were present. Kublai Khan had already met Haiyun in 1242 and been swayed towards Buddhism.
Genghis Khan’s decree exempting Daoists (xiansheng), Buddhists (toyin), Christians (erke’üd) and Muslims (dashmad) from tax duties were continued by his successors until the end of the Yuan dynasty in 1368. All the decrees use the same formula and state that Genghis Khan first gave the decree of exemption. Kublai Khan’s 1261 decree in Mongolian appointing the elder of the Shaolin monastery uses the same formula and states “Činggis qan-u jrlg-tur toyid erkegü:d šingšingü:d dašmad aliba alba gubčiri ülü üjen tngri-yi jalbariju bidan-a irüge:r ögün atugai keme:gsen jrlg-un yosuga:r…ene Šaolim janglau-da bariju yabuga:i jrlg ögbei” (According to the decree of Genghis Khan which says may the Buddhists, Christians, Daoists and Muslims be exempt from all taxation and may they pray to God and continue offering us blessings…I have given this decree to the Shaolin elder to carry it). According to Juvaini, Genghis Khan allowed religious freedom to Muslims during his conquest of Khwarezmia “permitting the recitation of the takbir and the azan“. However, Rashid-al-Din states there were occasions when Genghis Khan forbade Halal butchering. Kublai Khan revived the decree in 1280 after Muslims refused to eat at a banquet. He forbade Halal butchering and circumcision. The decree of Kublai Khan was revoked after a decade. Genghis Khan met Wahid-ud-Din in Afghanistan in 1221 and asked him if the prophet Muhammad predicted a Mongol conqueror. He was initially pleased with Wahid-ud-Din but then dismissed him from his service saying “I used to consider you a wise and prudent man, but from this speech of yours, it has become evident to me that you do not possess complete understanding and that your comprehension is but small”.