Shabbos is the root of all tranquility. Avraham's life of “weekday” movement is crowned with the “Shabbos” of refraining from slaughtering his son Yitzchak. Ahavah (love) is expressed in movement. Yirah (fear) is expressed by motionless. Yitzchak came from Avraham's aspect of motionless and yirah. The restlessness of Avraham was the outcome of a childhood of skepticism and doubt. Yitzchak was born into a world of faith, conducive to forming a nature of fear and stillness.