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Machloket · Bekhorot 50 · בכורות נ׳
The Price of Redemption: Sixteen Dinars or Twenty?
When the Sages expanded the biblical sela by a sixth, did the price of redeeming a firstborn son increase as well?
The Weight of the Biblical Shekel
The Torah requires a father to redeem his firstborn son by giving five silver selaim (shekels) to a kohen (priest). Rava explains that the original biblical sela was worth three and one-third silver dinars. The Torah states that a shekel equals twenty geirahs (translated as ma'ot), and six ma'ot constitute a dinar,.
Later, the Sages augmented the sela by one-sixth, setting its standard at twenty-four ma'ot, or four complete Tyrian dinars,. They derived authority to increase the coin from the biblical term "shall be",.
סִילְעִים דְּאוֹרָיְיתָא תְּלָתָא וְתִילְתָּא הָוֵי, דִּכְתִיב: ״עֶשְׂרִים גֵּרָה הַשֶּׁקֶל״, וּמְתַרְגְּמִינַן: ״עֶשְׂרִין מָעִין״, וְתַנְיָא: שֵׁשׁ מָעָה כֶּסֶף דִּינָר.The biblical sela coins are each three and one-third dinars in weight, as it is written: 'The shekel is twenty gera,' and we translate it as twenty ma'a, and it is taught: Six silver ma'a equal a dinar. (Bekhorot 50a:3)
Rav Ashi's Baseline Calculation
The Gemara records a practical disagreement regarding this payment between two leading scholars. Rav Ashi sent seventeen silver dinars to Rav Acha the son of Ravina, a kohen, for פדיון הבן (redemption of the firstborn son),. He requested that Rav Acha refund one-third of a dinar.
Five biblical selaim, at three and one-third dinars each, amount to sixteen and two-thirds dinars,. Rav Ashi held that redemption requires only this baseline biblical measure. In his view, rabbinic currency increases were never intended to expand a father's core personal liability.
רַב אָשֵׁי שַׁדַּר לֵיהּ שִׁבְסַר זוּזֵי לְרַב אַחָא בְּרֵיהּ דְּרָבִינָא בְּפִדְיוֹן הַבֵּן, שְׁלַח לֵיהּ: לִישַׁדַּר לִי מָר תִּלְתָּא יַתִּירְתָּאRav Ashi sent seventeen dinars to Rav Aḥa, son of Ravina, for the redemption of the firstborn son; he sent him: Let the Master send me back the extra third. (Bekhorot 50a:7)
Rav Acha's Demand for Twenty Dinars
Rav Acha the son of Ravina refused the refund and demanded additional money. He told Rav Ashi to deliver three more dinars to reach twenty dinars in total,.
Rav Acha reasoned that once the Sages increased the sela, the obligation required twenty complete dinars,. Scripture itself authorized the expansion of the sanctuary coin. Therefore, the official standard became fixed, and five selaim can never be fulfilled with less than twenty dinars.
שְׁלַח לֵיהּ: לְשַׁדַּר לִי מָר תְּלָתָא אַחֲרִינָא דְּאוֹסִיפוּ עִילָּוַיְיהוּ!He sent back to him: Let the Master send me the other three dinars that they added to them! (Bekhorot 50a:7)
What Turns on the Dispute
Beyond the difference of three and one-third dinars, this dispute explores how rabbinic currency expansions affect biblical law. Did the Sages permanently redefine the statutory standard for all biblical monetary mitzvot?
Or did the augmentation apply only to Temple dues like the half-shekel, leaving private obligations at their biblical base? Under Rav Acha's approach, a debtor or father must always pay according to the updated sanctuary valuation.
The Halachic Conclusion
The halacha is decided in accordance with Rav Acha the son of Ravina. Once the Sages augmented the coin, their measure became the permanent legal standard for all five-sela payments.
A father must give five full Tyrian selaim, which amount to twenty complete silver dinars,. Paying only the original biblical baseline of sixteen and two-thirds dinars does not fulfill the mitzvah.
A father must give twenty complete silver dinars for the redemption of his firstborn son, as the rabbinic augmentation permanently established the value of the five selaim.