俱舍論頌疏論本 23.73

23.73

離八地向三者，第三向也。謂先凡位斷欲修惑第九品盡，或斷初定一品，乃至斷無所有處惑盡，名離八地。此有六十四人，謂斷欲第九品為一人，斷上七地各九品惑各有九人，七九六十三，兼前一人，成六十四人。此六十四人至見道中名第三向也，趣不還果故。

Regarding 'detached from the eight grounds, one enters upon the third': this is the third enterer. That is to say, in the prior stage of an ordinary person, having completely abandoned the ninth category of defilements of cultivation of desire, or having abandoned one category of the first dhyāna, up to completely abandoning the defilements of the stage of nothingness, this is called 'detached from the eight grounds'. There are sixty-four such persons: abandoning the ninth category of desire makes one person; abandoning the nine categories of defilements in each of the seven higher grounds has nine persons each, seven times nine making sixty-three, which, combined with the previous one person, makes sixty-four persons. When these sixty-four persons reach the path of seeing, they are called enterers upon the third [fruit], because they tend toward the fruit of non-returner.