Musar על קידושין 61:12

From all the above it is clear that there never has been a Jew who was able to perform all the commandments listed in the Torah. Even the patriarchs, of whom our sages said they kept the entire Torah, (Yuma 28), observed only what they were able to. They had not been commanded to do so. They are referred to as the מרכבה, the carrier of the Divine entourage, even though their performance of the commandments was of a lower order because they were not an act of obedience to G–d.