Rashi on Exodus 20:12/רש"י על שמות כ׳:י״ב

1למען יארכון ימיך THAT THY DAYS MAY BE LONG — If thou honourest them they will be long, and if not, they will be shortened — for the words of the Torah may be explained as concise statements: from what is included in a positive statement we may infer the negative and from what is included in a negative statement we may infer the positive (Mekhilta).