Isaac ( /ˈaɪzək/;Hebrew: יִצְחָק, Modern Yitsẖak Tiberian Yiṣḥāq, ISO 259-3 Yiçḥaq, "he will laugh"; Yiddish: יצחק, Yitskhok; Ancient Greek: Ἰσαάκ, Isaak; Latin: Isaac; Arabic: إسحاق‎ or Arabic: إسحٰق‎ʼIsḥāq) as described in the Hebrew Bible, was the only son Abraham had with his wife Sarah, and was the father of Jacob and Esau. Isaac was one of the three patriarchs of the Israelites. According to the Book of Genesis, Abraham was 100 years old when Isaac was born, and Sarah was beyond childbearing years.

Isaac was the only biblical patriarch whose name was not changed, and the only one who did not leave Canaan. Compared to those of Abraham and Jacob, Isaac's story relates fewer incidents of his life. He died when he was 180 years old, making him the longest-lived patriarch.

The anglicized name Isaac is a transliteration of the Hebrew term Yiṣḥāq which literally means "He laughs/will laugh."Ugaritic texts dating from the 13th century BCE refer to the benevolent smile of the Canaanite deity El. Genesis, however, ascribes the laughter to Isaac's parents, Abraham and Sarah, rather than El. According to the biblical narrative, Abraham fell on his face and laughed when Elohim imparted the news of their son's eventual birth. He laughed because Sarah was past the age of childbearing; both she and Abraham were advanced in age. Later, when Sarah overheard three messengers of the Lord renew the promise, she laughed inwardly for the same reason. Sarah denied laughing when Elohim questioned Abraham about it.

Isaac ben Jacob Alfasi ha-Cohen (1013 - 1103) (Hebrew: ר' יצחק אלפסי) - also known as the Alfasi or by his Hebrew acronym Rif (Rabbi Isaac al-Fasi), was a Talmudist and posek (decider in matters of halakha - Jewish law). He is best known for his work of halakha, the legal code Sefer Ha-halachot, considered the first fundamental work in halakhic literature. He was born in the Algerian city Al Qal'a of Beni Hammad, but spent the majority of his career in Fes, and is therefore known as "Alfasi" ("of Fes" in Arabic).

Alfasi was born in Al Qal'a of Beni Hammad, the capital city of the Hammadid rulers of central Maghreb. He studied in Kairouan, Tunisia under Rabbeinu's Nissim ben Jacob, and Chananel ben Chushiel the recognized rabbinical authorities of the age. Rabbeinu Chananel trained Alfasi to deduce and to clarify the Halakha from Talmudic sources, and Alfasi then conceived of the idea of compiling a comprehensive work that would present all of the practical conclusions of the Gemara in a clear, definitive manner. To achieve this goal, he worked for ten consecutive years in his father-in-law's attic.