四分律行事鈔資持記 3.571

3.571

八中經文，初明上行。下極邊者，更無過故；此望世間，故云極下；若於聖道，則為最上，故名上行，亦號聖種。彼下，次示兩根，初是上根。族姓子，謂上姓貴族。為義者，即下厭患生死等。受謂信奉。若下，即下根。思欲者，即經三種不善思惟，所謂思惟五欲，思惟瞋害，思惟欺誑等。

In the eighth, in the sūtra text, first it explains the supreme practice. "Extremely low and marginal" means that nothing exceeds it; looking at it from the perspective of the worldly, it is therefore called extremely low; but with respect to the noble path, it is the highest, and hence is called the supreme practice, and is also called the noble lineage (āryavaṃśa). From "That" below, next it shows the two faculties: first is superior faculties. "Sons of good family" refers to noble clans of high birth. "For the sake of the goal" refers to loathing saṃsāra, etc., below. "Accepting" means having faith and practicing. From "If" below is the inferior faculty. "Thinking of desire" refers to the three kinds of unwholesome thoughts in the sūtra: namely, thinking of the five desires, thinking of malicious harm, thinking of deceit and fraud, etc.