Midrash sobre Exodo 16:23

A parable: To what is this matter to be compared? To a man who had precious utensils. And he did not desire to give them as an inheritance except to his son; likewise with the Holy One, blessed be He. The day of blessing and holiness which was before Him, He did not desire to give it as an inheritance except to Israel. Know that it is so ! Come and see ! for when the Israelites went forth from Egypt, whilst yet the Torah had not been given to them, He gave them the Sabbath as an inheritance. Israel kept two Sabbaths whilst as yet the Torah had not been given to them, as it is said, "And thou madest known unto them thy holy Sabbath" (Neh. 9:14). And afterwards He gave them the Torah, as it is said, "And commandedst them commandments, and statutes, and Torah by the hand of Moses, thy servant" (ibid.).