俱舍論疏 14.132

14.132

論「若有能持至心縱逸故」，受齋有二事：一自憶受近住戒、二於世間深生厭離。若非時食，二事俱無。

The commentary states: "If one is able to maintain [...] the mind becomes lax", in receiving upavāsa there are two things: first, personally remembering that one has received the upavāsa precepts; second, giving rise to profound revulsion toward the mundane world. If one eats at improper times, both things are lost.