四分律行事鈔資持記 3.185

3.185

二部，標中。謂檀越通施僧尼，隨來者得，故云互正。言四種者，謂二部僧得二部現前，各有時非時故。

In the statement of the two orders: it means that the dānapati gives generally to both monks and nuns, and whoever comes receives it, hence it is called "mutual principal." Speaking of "four kinds" refers to the two orders' [property] acquired by the Saṃgha and the two orders' [property given to those] present, each having timely and non-timely.