四分律行事鈔資持記 3.819

3.819

出寺法中，初結前。所下，正示，初教禮辭。凡下，令捨施。金剛堅利之寶，伽藍福業之地，故以喻焉。

In the rules for leaving the monastery, first, the preceding is concluded. 'That which...' onwards directly provides instruction; first, it teaches bowing in farewell. 'Whenever...' onwards instructs to renounce and give: vajra is a hard and sharp jewel, and the saṅghārāma is a place of merit, so they are used as metaphors.