Following giving commentary in "Kanmuryoju-kyosho" (also known as Kangyosho) (Commentary on the Meditation Sutra) by Shandao, and "Senchaku Hongan Nenbutsu-shu" (also known as Senchaku-shu) (Passages on the Selection of the Nenbutsu in the Original Vow) by Honen, Shinran stated in 'Gyo no maki' (a theme of Practice) of "Ken Jodo Shinjitsu Kyogyosho Monrui" (also known as "Kyogyoshinsho") (Selected passages revealing the true teaching, practice and attainment of the Pure Land) that the righteous practice is to call the name of Buddha, regarding the calling of 'Namu Amida Butsu' as the most righteous and important practice (Shojo no gyo) next to wishes by Amida Buddha.
善導の『観無量寿経疏』（『観経疏』）・法然の『選択本願念仏集』（『選択集』）に釈されたのを受けた親鸞は、『顕浄土真実教行証文類』（『教行信証』）の「行巻」に、正定の業とはすなはちこれ仏の名を称するなり。と、「南無阿弥陀仏」と称名する事こそが、正行の中で、阿弥陀仏の願に準じた一番重要（正定の業）であるとのべた。