Or HaChaim on Exodus 20:12/אור החיים על שמות כ׳:י״ב

1 למען יאריכון ימיך, "so that your days will be long, etc." The expression יאריכון implies that this will be a natural consequence; it is not a reward by G'd. Had it been intended as a reward, The Torah would have had to write something like: "I will lengthen your life, etc." The Torah may have taught us that the miraculous feature which attends performance of honouring father and mother is that persons doing so will enjoy long life. There are several commandments which are associated with miraculous phenomena; in all such cases this is not part of the reward for performing them.