Sforno on Deuteronomy 6:21/ספורנו על דברים ו׳:כ״א

1עבדים היינו, seeing that during the many years of our being slaves we could not attain the degree of perfection G’d had in mind for us to attain, He performed miracles in order to lead us out and to bring us to the land in which we could attain this degree of perfection.