The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
42. But with a view to the efforts made (by the soul) (the Lord makes it act), on account of the (otherwise resulting) purportlessness of the injunctions and prohibitions, &c.
The word 'but' removes the objections started.--The Lord makes the soul act, having regard to the efforts made by it, whether meritorious or non--meritorious. Hence
there is no room for the objections raised. Having regard to the inequality of the virtuous and vicious actions of the souls, the Lord, acting as a mere occasional cause, allots to them corresponding unequal results. An analogous case is furnished by rain. As rain constitutes the common occasional cause for shrubs, bushes, corn, and so on, which belong to different species and spring each from its particular seed--for the inequality of their sap, flowers, fruits, and leaves results neither when rain is absent nor when the special seeds are absent--; so we also must assume that the Lord arranges favourable or unfavourable circumstances for the souls with a view to their former efforts.--But if the activity of the soul is dependent on something else, this having regard (on the part of the Lord) to former effort is inappropriate.--By no means, we reply: for although the activity of the soul is not independent, yet the soul does act. The Lord indeed causes it to act, but it acts itself. Moreover, the Lord in causing it to act now has regard to its former efforts, and he caused it to act in a former existence, having regard to its efforts previous to that existence; a regressus against which, considering the eternity of the samsâra, no objections can be raised.--But how is it known that the Lord has regard to the efforts made (in former existences)?--The Sûtra replies: from the purportlessness, &c., of injunctions and prohibitions. For thus (i.e. if the Lord has regard to former actions) injunctions such as 'he who is desirous of the heavenly world is to sacrifice,' and prohibitions such as a Brâhmana must not be killed,' are not devoid of purport. On the other alternative they would be without purport, and the Lord would in fact be enjoined in the place of injunctions and prohibitions 1, since the soul would be absolutely dependent. And then the Lord might requite with good those who act according to the injunctions, and with evil men doing what is forbidden; which would
subvert the authoritativeness of the Veda. Moreover, if the Lord were absolutely without any regard, it would follow that also the ordinary efforts of men are without any purport; and so likewise the special conditions of place, time, and cause. And also the difficulty mentioned above 1 would present itself.--All these latter difficulties the Sûtrakâra comprises in his '&c.'
60:1 Îsvara eva vidhinishedhayoh sthâne niyugyeta yad vidhinishedhayoh phalam tad îsvarena tatpratipâditadharmâdharmanirapekshena kritam iti. Bhâ.
61:1 I.e. the objectionable assumption that men have to undergo consequences not resulting from their own former actions.