The theological basis for the Pure Land Refuge Aspiration rests on the Larger Sukhavativyuha Sutra's account of the bodhisattva Dharmakara, who is said to have made a series of vows, most famously the eighteenth, promising that anyone who sincerely calls on his name with faith and desires rebirth in his future Pure Land will attain it, before completing immeasurable ages of practice and becoming the Buddha Amitabha, whose realm of Sukhavati is understood to now exist precisely as the vows described. The aspiration to be reborn there therefore rests logically on the claim that Dharmakara's vows were successfully fulfilled, a claim central enough to Pure Land theology that different schools within the broader Pure Land movement have developed distinct positions on exactly how much personal spiritual effort, if any, is still required from the practitioner given that the enabling vow has already, according to the tradition, been completed on their behalf.
Japanese Pure Land teachers such as Honen and his student Shinran developed particularly influential and, in Shinran's case, particularly radical positions on this question, with Shinran's Jodo Shinshu tradition emphasizing reliance on Amitabha's vow so completely that even a single sincere recitation, or even the arising of faith without any recitation, was held sufficient, a position that shifted the aspiration's emphasis from cumulative practice toward trust in a completed act.