ISAAC (Hebr. yizhak, more rarely yishak, "the laugher"; LXX. Isaak, Vulg. Isaac): the son of Abraham and Sarah, who served as an object for testing his father’s faith and obedience. He was born (according to P) in Abraham’s hundredth year and in Sarah’s ninetieth. Gen. xxi. 6 (E?)--cf. xvii. 17 (P), xviii. 12 sqq. (J)--brings the name into connection with his birth. Abraham’s obedience was shown in the circumcision of the boy eight days after his birth (Gen. xxi. 4, P), and in his readiness to sacrifice, at God’s command, this son for whom he had so ardently longed (chap. xxii.). Isaac in this submitted to the will of his father, just as he did later in his marriage with Rebekah, although he was then forty years old. Few details are given in regard to the remainder of Isaac’s life, and he appears as a rather weak copy of his father. He manifested a lesser fondness for journeying, since his travels were confined to the southern portion of the land, the Negeb, and the neighboring territory. In this desolate region, the well Lahai-roi (Gen. xxiv. 62; the modem Munailah), Gerar, the Philistine city (xxvi. 1; the modern Jerar), the valley of Gerar (xxvi. 17), Beersheba (xxvi. 23), and finally Hebron (xxxv. 27), are places where he sojourned for a time. When at Gerar, according to Gen. xxvi. 7 sqq., he had an experience with King Abimelech similar to his father’s (Gen. xx. 1 sqq., E, xii. 10 sqq., J). The similarity of the three accounts does not necessarily imply that they are variations of the same incident; but borrowings and substitutions may have taken place in oral tradition.

Isaac was characterized, as contrasted with Abraham, by a certain advance in civilization. In Gerar he devoted himself both to the raising of flocks and herds and to agriculture. His food was game and his drink was wine, while Abraham obtained the latter only from some other prince. Isaac appeared always as pacifically inclined, yielding to his envious neighbors when they disputed with him the possession of wells, and yet he enjoyed a singular respect on the part of strangers, who considered it desirable to be on friendly footing with the "blessed of the Lord" (Gen. xxvi. 28 sqq.). The principal significance of Isaac is that he carried over the divine blessing of the covenant from Abraham to Jacob, the ancestor of Israel. After his wife had been for a long time barren (Gen. xxv. 21), twin children of very different characters, Esau and Jacob, were granted to him in answer to his prayer. Although the father clung to the elder, when old and blind he was forced by the stratagem of his wife to bestow upon his younger son, Jacob, the blessing which had been bequeathed to him by Abraham (Gen. xxvi. 3 sqq., 24). Isaac showed little independence either at home or abroad, in place of which his submission to the decrees of the Almighty gave him his position between Abraham the faithful and Jacob, the champion of the faith. In this trio Isaac represents that pious fidelity which guards the inherited blessing, more occupied with its preservation than with any idea of further gain. For later Jews he appears as "the chief of the bound and tortured" (Midrash to Esther), that is, the prototype of martyrs.

The story of Isaac is made up from the three Pentateuchal sources, which agree essentially in their narratives and guarantee the historical character of Isaac’s personality. His name does not yield to the explanation that it belonged to a divinity or a tribe, the significance "he laughs" being inappropriate to both.

The designation of God as "the fear of Isaac" (Gen. xxxi. 42, 53) is peculiar. Since this "fear" was sworn by, it must mean "divinity," corresponding to the Greek sebas in the sense of sebasma, "an object of awe or reverence."