Or HaChaim on Leviticus 18:25/אור החיים על ויקרא י״ח:כ״ה

1 ותטמא הארץ, and the land became defiled, etc. The Torah here intends to tell us something similar to what we have read in the Zohar volume 3 page 53 that the actions of Israel determine the amount of spirituality in our world both positively and negatively. Our sages in Avot 4,11 say that a spiritually positive force is created with the performance of every commandment, whereas a spiritually negative force is created due to a sin being committed. The Torah alludes to this concept when it wrote ואפקוד עונה עליה, "I punished it for its iniquity, etc." This is in line with Jeremiah 2,19 that "your wickedness caused you to be disciplined." Performance of sinful deeds keeps strengthening the accuser against us at the celestial court. Man will be paid in accordance with his deeds. Tomer Devorah chapter 1 describes this payment as the creation of a destructive "angel" who will in due course repay the sinner who had created him. This "angel" loses potency in direct proportion to the afflictions experienced by its victim, so that once the victim has experienced sufficient pain the "angel" expires by itself. G'd deals with everyone absolutely fairly, treating each person individually. The meaning of ואפקד עונה is that the sin itself and its effect is visited upon the sinner. I have already explained why the Torah uses the singular. According to our approach it is possible that the various destructive "angels" man creates due to his sins are activated one at a time and not simultaneously and that this is why the Torah describes the sin in the singular.