Rambam, Mishnah, Chulin 7:6

You must know that whatever we do or refrain from doing today, we do only because of God's command by way of Moshe, and not because of God's command to the prophets that preceded him. For example, we refrain from eating a limb removed from a living animal not because God forbade this to the descendants of Noach, but because God forbade it to us when He commanded us at Sinai that a limb removed from a living animal continues to be forbidden… You see that [the Sages] said (Makkot 23b): "Six hundred and thirteen mitzvot were told to Moshe at Sinai," and all these are included among the mitzvot.