Q. The Jews knew that G-d brought them out of Egypt where they were slaves. Why was it necessary for G-d to introduce himself for the first time at Mount Sinai, saying that it was HE who brought them out of slavery?
A. The redemption from Egyptian bondage is something that every Jew experienced personally and it was fresh in their minds and it had a personal meaning to every Jew. It was necessary for G-d to identify Himself as the miracle worker in the freedom the Jews got, because G-d is an abstract G-d who you cannot see. The human being's concept of G-d depends on the circumstances in which G-d manifests Himself.
