四分律行事鈔資持記 2.217

2.217

七要期者。與形俱何異？答：形俱隨報，要期不定。疏云：如十大受，及八分齊；要心所期，如誓而起。（十受出《勝髮》，八齊開自誓。）文舉善事，惡亦同然。

Seventh, as for "fixed-period [karma]": how does it differ from [karma that] "coexists with the physical form"? Answer: Coexisting with the physical form follows the lifespan, whereas a fixed period is not indeterminate. The Commentary states: "Like the ten great vows and the eightfold limits; that which is set by the resolute mind arises in accordance with the vow." (The ten vows are from the Śrīmālādevī-sūtra; the eightfold limits allow self-vowing.) The text cites wholesome matters; unwholesome matters are likewise the same.