The Sages teach that Abraham fulfilled the mitzvot even before the Torah was given at Sinai.

We find that Abraham our patriarch observed the entire Torah before it was given, as it is stated: “Because Abraham heeded My voice, and observed My commission, My commandments, My statutes, and My laws” (Genesis 26:5). Rava, and some say Rav Ashi, said: Abraham our patriarch fulfilled even the rabbinic ordinance of joining of cooked foods, as it is stated: My laws, in the plural; both the Written Law and the Oral Law. (Mishna Kiddushin 4:14; Yoma 28b)