大毘盧遮那成佛經疏 2.58

2.58

第廿九「云何狗心？謂得少分以為喜足」者，以狗以薄福因緣，所期下劣故，遇得少分麁鄙之食便生喜足。若稍過於此者，則非本所望。此心亦爾，聞少分善法，便以為行不可盡，不復更求勝事。此聲聞種習所生也。以增上意樂，為所對治。乃至心如大海，少亦不拒、多亦不溢。

The twenty-ninth: "What is the dog mind? It is being satisfied with obtaining a small portion." Because a dog has petty merit and low expectations, when it happens to obtain a small portion of coarse and wretched food, it is content and satisfied. If something slightly exceeds this, it is beyond its original expectations. This mind is also like this: hearing a small portion of wholesome teachings, it considers its practice inexhaustible and no longer seeks superior attainments. This arises from the habitual tendencies of the śrāvaka lineage. Developing superior resolve serves as its antidote, so that one's mind becomes like the great ocean—neither refusing what is small, nor overflowing with what is abundant.