Did the Patriarchs and Matriarchs Keep the Entire Torah?

(1) The two angels arrived in Sodom in the evening, as Lot was sitting in the gate of Sodom. When Lot saw them, he rose to greet them and, bowing low with his face to the ground, (2) he said, “Please, my lords, turn aside to your servant’s house to spend the night, and bathe your feet; then you may be on your way early.” But they said, “No, we will spend the night in the square.” (3) But he urged them strongly, so they turned his way and entered his house. He prepared a feast for them and baked unleavened bread, and they ate.

ומצות אפה AND HE BAKED UNLEAVENED BREAD —It was Passover (Genesis Rabbah 50).

(1) When Isaac was old and his eyes were too dim to see, he called his older son Esau and said to him, “My son.” He answered, “Here I am.” (2) And he said, “I am old now, and I do not know how soon I may die. (3) Take your gear, your quiver and bow, and go out into the open and hunt me some game.

"Take your gear": ... Isaac said to Esau, “Sharpen your knife and slaughter an animal according to the regulations so that you may not give me to eat נבלה” (i.e. the flesh of animal that is not killed according to the ritual rules) (Genesis Rabbah 65).

The LORD had appeared to [Isaac] and said, “... I will be with you and bless you... inasmuch as Abraham obeyed Me and kept My charge: My commandments, My laws, and My teachings.”

Rav said: Avraham Avinu kept the entire Torah, as it is stated in Genesis 26:5, "Since Avraham listened to My Voice..."

Rav, or Rav Ashi, said: Avraham Avinu kept even eruvei tavshilin... [that is], he kept both the Written Torah and the Oral Torah...

(5) And he kept My charge:..."My charge" - precautionary decrees, for example, second degree prohibitions of [marriage between relatives] and the rabbinic prohibitions on Shabbat...My ordinances" - matters which the evil inclination and the idolaters argue against, for example the eating of pig and the wearing of garments made of a mixture of wool and linen (shaatnez) - for which there is no reason but that the King decreed His enactment upon His subjects; "and My laws" - to include [with the written Law also] the Oral Law, [and] the laws [given by God] to Moshe from Sinai. And if so, all [of Rashi's approach here], is built upon the opinion that Avraham observed and kept the Torah before it was given...

​ And one can ask, "If so, how did Yaakov set up a pillar (Genesis 28:18), and marry two sisters - and according to the opinion of the rabbis (Bereshit Rabbah 74:11), four sisters; and Amram marry his aunt (Exodus 6:20)...?

...what appears to me from the opinion of our rabbis is that Avraham learned the entire Torah from holy inspiration, and was occupied in its [study] and in the reasons for its commandments and its secrets, and he kept all of it as one who is not commanded and does...

And on the level of the simple meaning, we can say that "My charge" is faith in Divinity, that he believed in the unique God and that he kept this charge in his heart and he differed from the idolaters about it and called in the name of the Lord to bring back many to the service [of God]; "My commandments" is like all that He had commanded him, in 'Go forth from your land,' and with the raising of his son [for a sacrifice] and the sending away of 'the maidservant and her son'; "My ordinances" is going in the ways of God, to be 'graceful and merciful' and 'to do righteousness and justice' and 'to command his children and his household' about [these things]; "and My laws" is circumcision on himself and on his children and servants, and all of the commandments of the Children of Noach, as they are the law to them.

(5) וישמור משמרתי, he also did the very things which I Myself am in the habit of doing, such as to perform deeds of loving kindness. Also, Avraham warned the potential sinners to improve their ways, something that is of utmost importance to Me. This is what he did every time the Torah records him as קרא בשם ה', “he proclaimed the name of the Lord.” He also observed My revealed commandments מצותי, חוקותי, ותורותי, “the seven laws I laid down for all of mankind.” As a result of all this, he did not only preach to his fellow man but he practiced what he preached. Due to his possessing this virtue he became a model human being for others to emulate.