Tafsir of Al-Ghashiyah 88:9

"For her striving," meaning for the work she performed in the abode of this world. It is connected to the words of the Almighty: "Satisfied" (rāḍiyah). The advancement [of the prepositional phrase] is for the sake of importance, while observing the rhyme scheme [of the verse]. The particle lam is not for causation; rather, it is like the lam in the expression: "I am satisfied with such-and-such" (raḍītu bi-kadhā). It has been said: "Satisfied with her striving." Some researchers have stated that it serves to strengthen the transitive quality of the adjective itself. For this reason, Sufyan said regarding it—as reported by Ibn Abi Hatim—"She is satisfied with her work." Her satisfaction with it is a metonymy or a metaphor indicating that its consequence is praiseworthy and that she is rewarded for it with the greatest and best of rewards.

It has also been said that there is an implied genitive construction in the discourse, meaning: "Satisfied with the reward of her striving." It is further permitted that the lam is for causation, meaning: "Because of her striving in the obedience of Allah the Almighty, she is satisfied, as she has been brought and given good." However, this [latter interpretation] is not strong.