The second perek (=chapter) of Masechet Arakhin began on yesterday’s daf (=page) beginning with a discussion of a law that was not mentioned in the opening perek.
If a poor person takes upon himself to pay the erekh – the value of a person – there is a unique law of heseg yad – or the ability to pay. As opposed to an ordinary vow to the Temple, where the person is obligated to pay his commitment in full, and neither a kohen nor the treasurer of the Temple can offer to free him of his obligation, in nidrei arakhin, the Torahincludes a clause that specifically gives the kohen the right to establish the man’s ability to pay (see Vayikra 27:8) so that someone who has limited means will only pay what he can afford. The Mishnah teaches that the adjusted value established by the kohen cannot be less than a sela or more than 50 sela.
What if the erekh that the poor man accepts on himself was more than five sela, but he only has five sela? Rabbi Me’irrules that he need not pay more than a single sela; the Sages rule that he must pay everything that he has. The Mishnah concludes: “there is no valuation of less than one sela nor more than fifty sela.”
The Gemara on today’s daf asks why the Mishnah needs to include the final clause “there is no valuation of less than one sela nor more than fifty sela,” which appears to be redundant. The Gemara explains that this establishes the stam Mishnah – the simple, and therefore authoritative ruling of the Mishnah – in accordance with the opinion of the Sages, rather than Rabbi Me’ir.
The sela used in the Mishnah is the biblical shekel, which was silver weighing 20 gera (see Vayikra 27:25). According to the Rambam their weight was 384 grains of barley or about 17 grams of pure silver.