Sforno on Deuteronomy 5:29/ספורנו על דברים ה׳:כ״ט

1ושמרתם לעשות, seeing that things have developed in this fashion it is no more than a minimal request that you observe and carry out G’d’s commandments,

2ולא תסורו ימין ושמאל, neither to add to them even if your intentions are good, nor to detract from them.