The LORD appeared to Isaac just as He had appeared to Abraham. He told him, "I will establish the oath which I swore to your father Abraham" (Genesis 26:3). He restated the promise to multiply his descendents, to give them the land and to bless all nations through them "because Abraham obeyed Me and kept My charge, My commandments, My statutes and My laws" (Genesis 26:5). Isaac was inheriting the Abrahamic blessing because Abraham had merited God's favor.
How did Abraham keep God's charge, commandments, statutes and laws? The commandments of God's Torah—His divine law—had not been given yet. Did Abraham know all the laws of the Torah given through Moses at Mount Sinai? If not, how could he be said to have kept them?
Rashi claims that this means Abraham kept the entire Torah and the oral traditional law of Judaism. That seems like a stretch, but what does it really mean? What laws did Abraham keep?
Some say that Abraham knew the laws of God because they had been handed on to him through the line of Noah. Other sources imagine that perhaps he had a book written by Enoch that contained the laws that would be given at Sinai. Still others say that God communicated all the laws to him in advance of giving the Torah at Sinai.
Another opinion has it that he kept all the laws he knew, such as the basic laws of morality and stipulations God had revealed, like circumcision.
Whatever the case may have been, it is important to note that Abraham's righteousness was not a matter of faith without obedience. Anyone who teaches that observing God's laws is contrary to the life of faith should consider this verse. The Bible says that God passed the blessings and promises to Isaac because Abraham obeyed God's laws. This is in keeping with what the Apostle Paul teaches when he says, "Is the Torah then contrary to the promises of God? May it never be!" (Galatians 3:21). James, the brother of Yeshua, shows that the life of faith results in obedience to God's laws:
You see that faith was working with his works, and as a result of the works, faith was perfected. (James 2:22)
Keeping God's commandments is an important part of practicing the faith of Abraham: "Yeshua said to them, 'If you are Abraham's children, do the deeds of Abraham'" (John 8:39).