阿彌陀經通贊疏 3.77

3.77

贊曰：第二彰其勝益。念佛發願故，一即彼佛冥加，二即此佛潛衛，遂令求道之心不退、願生之志不轉，故言不退轉。若已發願已得不退，今發願者即現在今得不退，當發願者當得不退轉也。

The Praise states: The second reveals its superior benefits. Because of recollecting the Buddha and making the vow, first, there is the unseen assistance of that Buddha, and second, there is the hidden protection of this Buddha; consequently, their aspiration to seek the Path does not retrogress and their determination to be reborn does not turn back; hence it says 'non-retrogression'. If one has already made the vow, one has already attained non-retrogression; if one is now making the vow, one immediately attains non-retrogression in the present; if one will make the vow, one will attain non-retrogression in the future.