金剛經纂要刊定記 2.95

2.95

轉授天親者。有說云：以天親久習小乘、近從大教，要滌情執故轉授之，斷疑執，顯行位，正宗文中可見。

Regarding 'transmitted to Vasubandhu': Some say that because Vasubandhu had long practiced the Hīnayāna and had only recently turned to the Great Teaching, it was necessary to cleanse his emotional attachments; thus it was transmitted to him to sever doubts and attachments and make clear the stages of practice, as can be seen in the main text.