金光明最勝王經疏 4.179

4.179

贊曰：勸持也。如《法華經》第二敘佛恩深無能得報。〈囑累品〉云「唯受持經，即為報恩。」此亦如是。

The commentary says: This is the exhortation to uphold it. As the Lotus Sūtra (chapter 2) describes, the Buddha's kindness is profound and none can repay it; the "Entrustment" chapter says: "Only receiving and upholding the sūtra is repaying the kindness." This is also like that.