The earliest mission to China was carried out by the Church of the East, whose monks set their feet on the land of a spirited society represented by thousands of years of ancestral worship and fear of deities from Daoism, Buddhism, Confucianism, and other folk religions. This proposal aims to investigate Jingjiao’s surviving documents, particularly xuting mishi suojing 序聽迷詩所經 (Book of Righteous Mediator, hereafter Mediator), and study how its missionaries contextualized the Christian message in a culture that practices xiao 孝 (filial piety) and is permeated with all sorts of spirits. Some suggest—wrongly, I believe—that by accommodating Confucian ethics, the Jingjiao writers compromised the Christian teachings. This proposal argues that by following the example of Tatian, who composed the most prominent early gospel harmony, namely, Diatessaron, the Church of the East writer harmonized the Ten Commandments with Paul’s message in Romans 13:1-7 by tapping into the spirited world in Tang China. In this way, the creative and transformative power of the Holy Spirit is manifested. The proposed paper will first present the ancestral worship and the spirits that permeated ancient and medieval China. Then, I will analyze Mediator and investigate how the concepts of ancestors, filial piety, and the Holy Spirit interwoven while keeping an eye on Tatian’s Diatessaron. Finally, the implications of Jingjiao’s contextualized theology will be presented toward a constructive missional pneumatology in the third millennium.