והיה עקב תשמעון את המשפטים האלה ושמרתם ועשיתם אתם (ז-יב)
Rashi comments that people tend to pay more attention to those mitzvos and prohibitions which appear to them to be of greater importance whilst neglecting and treading underfoot (עקב) those of lesser consequence. This attitude is totally wrong. R’ Pinchos Roberts shlit’a explains that in the human body, the heart is viewed as more important than the kidneys, the lungs or the pancreas. Nevertheless, the body cannot function unless all those organs are healthy. Each one performs a specific task, without which life is imperiled. Similarly, the spiritual well-being of a Jew requires the performance of all mitzvos. Our Sages say that the 613 major organs and arteries are sustained by the 613 injunctions of the Torah - each one nourishes a unique and particular part of our spiritual system and therefore to neglect any command is injurious and foolhardy.
The Satan, too, is well aware of this fact and accordingly directs much of his attention towards persuading us to overlook “minor” mitzvos. The Torah forecasts that he will be successful. On the posuk in Bereishis (ג-טו): “He will strike you in the head, but you will smite him in the heel,” the Kli Yakar writes that Hashem was speaking to the serpent who represented the evil inclination after it enticed Adam into sin. Whenever the sly snake will try to ensnare a Jew to forsake crucial mitzvos, connoted by the word “head,” he will easily be overcome. But when he tries to inject his poison into the “heel” of a Jew and urge him to tread underfoot less significant laws, he will triumph. Unfortunately, just as poison can travel from the heel throughout the body, sins which seem trivial gradually erode the meticulous observance of more “consequential” commandments, and the condition becomes critical. It is, therefore, vital to be aware that any sin has a chain reaction and must be repressed at birth.