瑜伽師地論略纂 6.56

6.56

三欲中，「多用功力依緣諸欲，謂現前住所有諸欲」者，下四欲天欲，多依現前諸欲生起，用功念想，方從彼生。或復由業異熟，用功方治成熟故。

Among the three desires, "desires that rely on objects with great exertion, meaning all desires currently present": the desires of the lower four desire heavens mostly arise depending on currently present desires; only when one applies effort in thinking do they arise from them. Or again, it is because of the karmic fruition that one must apply effort to process and mature them.