瑜伽論記 11.421

11.421

基云：所得有退者顯行不定也，又不定者所作不純，有退者不能純進，又不定者尚懷猶預，有退者不能勝進故退也。

Ji says: That what is attained has retrogression demonstrates that their practices are undetermined. Furthermore, 'undetermined' means that what is performed is not pure, and 'having retrogression' means that they cannot progress purely. Again, 'undetermined' means that they still harbor hesitation, and 'having retrogression' means that, being unable to advance superiorly, they consequently retrogress.