Parashat Va-Yehi 5769/ January 10, 2009
the weekly Torah reading by the faculty of
On the Blessing for Sons*
Prof. Daniel Sperber, President
The Ludwig and Erica Jesselson Institute for Advanced Torah Studies
It has become a widespread and accepted custom to bless one’s children on Friday night with the blessing taken from this week’s reading: “G-d make you like Ephraim and Manasseh” (for sons, and for daughters, “God make you like Sarah, Rebekah, Rachel and Leah”), followed by the priestly blessing, “May the Lord bless you and keep you …” We shall not go into the history of this custom here, but only mention that it is quite late, being found in the prayer-book of Rabbi Jacob Emden.  We shall investigate another point, namely whether the blessing should be accompanied by laying one hand or two. This question is discussed by Rabbi Isaac Lapronti, in his book Pahad Yitzhak.  He wrote as follows:
I have seen some fastidious people who do not bless their disciples with both hands, and say that it should be done thus so as not to mix mercy with strict judgment.  I, however, used to bless those who were married with both hands, one for him and the other for his wife, and bachelors with one hand.
Both hands are place on their heads, as we find to be the case with all blessings. According to the custom of Moses, our magnanimous Teacher of blessed memory (Num. 27:23), in the same manner one ought always to bestow blessings, for the generous man is blessed (Prov. 22:9); likewise the priests, when they give the priestly blessing, raise both hands. And thus we find to be the case with the angels on the eve of the Sabbath, for the Sages said (Shabbat 119b) that when they bless a person they lay their hands on his head…and such was the practice of my father and teacher (R. Tzvi Ashkenazi), the gaon of blessed memory. And not as the boorish do, being fastidious about blessing particularly with only one hand.
It may be tentatively suggested that the custom of blessing with one hand stemmed from an attempt to emulate our patriarch Jacob, who in blessing Ephraim and Manasseh of course laid one hand on each, and ma'aseh avot siman la-banim--the deeds of the patriarchs set an example to be emulated by future generations. When this practice spread to certain communities, the rabbis sought to provide another reason for it and typically offered explanations based on mysticism.
Be that as it may, it is interesting that the practice of not blessing with both hands came to have the force of a prohibition in certain circles, and this approach was ascribed to the Vilna Gaon. This is how it was: Rabbi Barukh ha-Levi Epstein, author of Torah Temimah, recounts a story that he heard from a confidant of his, in these words: 
The Vilna Gaon blessed Rabbi
Yehezkel Landau, Dayyan
(rabbinic judge) of Vilna (author of Ha-Noda be-Yehudah)
at his wedding, placing one hand on the head of Rabbi
Yehezkel as he gave the blessing.
When asked about this, he responded that we
do not find substantiation for blessings to be given by laying both hands,
except for the case of the priests in the
Based on this, the author of Torah Temimah concluded that in practice it is actually forbidden to anyone who is not a priest to bless someone by laying both hands. This principle was accepted in certain circles and even cited in contemporary prayer-books attributed to the Vilna Gaon. 
Quite a different version of this story about the Vilna Gaon appears in Ma’aseh Alfas by Rabbi Ben Zion Alfas, as relayed to him by Rabbi Yehezkel Landau himself: 
I knew the gaon, Rabbi Yehezkel Landau, of blessed memory, head of the Rabbinical Court of Vilna, who, when he became a bridegroom, was brought by his father-in-law to the Vilna Gaon to be blessed. At the time the Vilna Gaon was sitting down to his second meal of the Sabbath, eating his kugel. When the Gaon sought to place his hands on the bridegroom’s head to bless him, the bridegroom, who was wearing a streimel, recoiled so that the Gaon not soil his streimel with his greasy hands from the kugel he had been eating, and so the Vilna Gaon only placed one hand on the streimel and blessed him. He (Rabbi Yehezkel Landau) lived to a ripe old age (until age ninety-one), and to his dying day did not wear eyeglasses when he studied; and all his life Rabbi Yehezkel Landau felt remorseful over having been so petty, caring more for his streimel than for the laying of hands by the Vilna Gaon.
This story evolved in the course of transmission, giving birth to the supposed proscription against blessing one’s sons by laying both hands. To this erroneous tradition a cautionary explanation was added that one must not lay more than one hand for mystic reasons.
The article relies on the article of Daniel Rabinowitz
 For further details, see Rabinowitz’s article, cited above.
Pahad Yitzhak ha-Shalem,
 This is
a kabbalistic motif that has had an impact on many a
custom, such as buttoning one’s outer garments with the right side always over
the left, so that mercy outweigh strict justice.
There is also the custom of clasping one’s
hands with the right hand always over the left, as well as the custom of not
interlacing one’s fingers, because that obscures the difference between mercy
and justice. Another mystic reason for
laying only one hand in the blessing was recorded by Rabbi Solomon
Rokach, a 17th century
Italian kabbalist (
Venice 1679, 32b-c): “The youngster is
blessed by laying a hand. This is
alluded to by the fact that the father’s hand contains 15 parts, matching the
15 letters in the Hebrew verse, ‘May the Lord bless you and keep you,’” as if
to say that the blessings in these three verses devolve on your head.
See the article by Moshe Halamish,
“Mekomah shel ha-
Kabbalah ba-Minhag,” in D.
 Torah Temimah, Numbers 6:23, par. 131.
 Siddur Aliyot Eliyahu, Machon Ma’adanei Asher 1999, p. 245; Siddur Ezor Alibo, ed. Rabbi Yehoshua Cohen, Kerem Eliyahu, Jerusalem 1995, p. 173.
 Ma’aseh Alfas, Bnei Brak 1975, p. 9.