When G-d informed Abraham that Sarah would have a son, his reaction was to laugh (“va’yitzchak” – Genesis 17:17). When Sarah heard about this prophecy, she laughed as well (ibid. 18:12). When Isaac was born, Sarah exclaimed, “G-d is making ‘laughter’ [tzchok] for me; whoever hears will laugh (yitzchak) for me (ibid. 21:6). G-d Himself said that her son will be called Yitzchak (ibid. 17:19) – a name that literally means “he will laugh.”
Yet, the Bible refers to this patriarch in four places as “Yischak” (Jeremiah 33:26, Amos 7:9, Amos 7:16, and Psalms 105:9). What’s the difference between “Yitzchak” and “Yischak”?
To answer this question, we must first explore the difference between their respective antecedents, “s’chok” and “tzchok.” The problem is that major Hebrew lexicographers like Menachem Ibn Saruk (920-970), Rabbi Yonah Ibn Janach (990-1955), and even Rabbi Shlomo Pappenheim (1740-1840) write that “s’chok” and “tzchok” mean the exact same thing.
Rabbi Pappenheim explains that the core meaning of “s’chok”/“tzchok” is laughter as an involuntary reaction to some sort of outside stimulus. Both words carry positive (laughing, playing, enjoying) and negative (deriding, mocking) connotations.
Rabbi Samson Raphael Hirsch (to Genesis 21:6) writes that the connotations are connected because mockery/derision is designed to elicit laughter – i.e., to get somebody to laugh at someone or something (see Malbim to Judges 16:25).
As an aside, Rabbi Hirsch (to Genesis 17:7) invokes the interchangeability of chet and ayin to explain how “tzchok” and “s’chok” are related to “tzaakah” and “zaakah” (crying out). He notes that these four roots represent man’s two reactions to dissonance and incongruence: laughter or crying. They are both ways for us to reconcile what we see with what we expect.
In any event, there seems to be no semantic difference between “s’chok” and “tzchok.” Of course, that raises the obvious question: Why, then, does the Bible sometimes refer to “Yitzchak” as “Yischak”?
Rabbeinu Bachaya (to Genesis 17:19 and Numbers 32:3) writes that Isaac’s name is really “Yitzchak,” but the prophets sometimes spelled his name with a sin/shin to allude to the fact that Isaac personifies the divine trait of judgment, which is likened to a raging fire (eish).
Interestingly, Rabbi Shmuel Feivish Kahane (a 17th century sage) in his work Leket Shmuel offers the exact opposite explanation. He writes that Isaac’s name should have really been written as “Yischak,” but since the presence of a sin/shin would have alluded to raging judgment from which the Jewish people couldn’t recover, the Torah spells the patriarch’s name with a tzadi.
Rabbi Yehuda Moscato (1530-1593) writes that in the future, Isaac’s name will change from “Yitzchak” to “Yischak” because the letter sin stands for sasson and simchah. He writes that this new name only appears four times in the Bible as a hint to the fact that the change will come only after the Jews complete four exiles (the last of which we are currently living in).
Rabbi Shmuel Borenstein (1855-1926) uses a variation of this idea to reconcile an apparent contradiction. The Talmud (Brachos 61b) and Sefer Yetzirah (ch. 5) imply that the spleen corresponds to man’s ability to laugh while the Tikkunei HaZohar (Tikkun #84) associates the spleen with sadness. To resolve this contradiction, Rabbi Borenstein stipulates that there are two types of laughter: legitimate, holy laughter and illegitimate, impure laughter.
The former is essentially reserved for the future, as Psalms 126:2 states, “Then [in the Messianic era], our mouths will fill with laughter (s’chok).” Until then, most laughter is but an illusion intended to mask sadness and despondency. Accordingly, the spleen can be associated with both laughter and sadness if we assume that the type of laughter it characterizes is the illegitimate laughter of this world, which is merely a cover for sadness.
Rabbi Borenstein explains that in the future, when schok will denote legitimate laughter, the patriarch Isaac’s name will transform from “Yitzchak” to “Yischak.” (The Arizal [Shaar HaPesukim to Isaiah 52:3] also offers an explanation of the Yitzchak-Yischak switch, but I don’t quite understand it.)
From other sources, it seems that Isaac’s original name was “Yischak,” which was later changed to “Yitzchak.” These sources relate that when the Jews cried out to G-d during their exile to Egypt, He asked the forefathers which of them was willing to sacrifice the numerical value of his name to save the Jewish people. Isaac volunteered and allowed G-d to change the sin (which holds a numerical value of 300) of his name Yischak into a tzadi (which equals 90).
The difference comes out to 210, which is why the Jews were redeemed from Egypt after 210 years. (This tradition is cited in numerous works including Imrei Noam [to Exodus 6:2], Pseudo-Rosh [to Exodus 6:1], Siddur Rokeach, Be’er Mayim Chaim [to Genesis 15:13], and Leket Shmuel [to Gen. 25:19].)
The Vilna Gaon (1720-1797), in his commentary to Safra d’Tzneusa (end of ch. 3), writes that each of the three patriarchs had two names – a lower name and a higher name. In light of the above, we can now better appreciate his assertion. “Yitzchak” was the lower name and “Yischak” is the higher name.
Sefer HaShem (ascribed to the Rokeach) fascinatingly notes that the gematria of “Avraham,” “Yischak,” and “Yeshurun” equal 2,448 (assuming a final mem equals 600 and a final nun equals 700) – the year the Torah was given at Mount Sinai.