阿彌陀經疏 1.43

1.43

如是下，總結。弟子者，學居師後故稱弟，解從師生故稱子，弟則顯師之謙讓，子乃明資之尊仰。

From “such as these” downward is the concluding summary. “Disciples”: because their learning ranks behind the master, they are called younger brothers; because their understanding is born from the master, they are called sons. “Brother” reveals the master’s modesty, and “son” makes clear the student’s reverence.