Reference for Arakhin 4:4
שָׁנִים בַּנִּדָּר כֵּיצַד, יֶלֶד שֶׁהֶעֱרִיךְ אֶת הַזָּקֵן, נוֹתֵן עֵרֶךְ זָקֵן. וְזָקֵן שֶׁהֶעֱרִיךְ אֶת הַיֶּלֶד, נוֹתֵן עֵרֶךְ יֶלֶד. וַעֲרָכִים בַּנֶּעֱרָךְ כֵּיצַד, אִישׁ שֶׁהֶעֱרִיךְ אֶת הָאִשָּׁה, נוֹתֵן עֵרֶךְ אִשָּׁה. וְאִשָּׁה שֶׁהֶעֱרִיכָה אֶת הָאִישׁ, נוֹתֶנֶת עֵרֶךְ אִישׁ. וְהָעֵרֶךְ בִּזְמַן הָעֵרֶךְ כֵּיצַד, הֶעֱרִיכוֹ פָּחוּת מִבֶּן חָמֵשׁ וְנַעֲשָׂה יוֹתֵר עַל בֶּן חָמֵשׁ, פָּחוּת מִבֶּן עֶשְׂרִים וְנַעֲשָׂה יוֹתֵר עַל בֶּן עֶשְׂרִים, נוֹתֵן כִּזְמַן הָעֵרֶךְ. יוֹם שְׁלֹשִׁים, כִּלְמַטָּה מִמֶּנּוּ. שְׁנַת חָמֵשׁ וּשְׁנַת עֶשְׂרִים, כִּלְמַטָּה מִמֶּנּוּ, שֶׁנֶּאֱמַר (ויקרא כז), וְאִם מִבֶּן שִׁשִּׁים שָׁנָה וָמַעְלָה אִם זָכָר, הֲרֵי אָנוּ לְמֵדִים בְּכֻלָּם מִשְּׁנַת שִׁשִּׁים. מַה שְּׁנַת שִׁשִּׁים כִּלְמַטָּה מִמֶּנָּה, אַף שְׁנַת חָמֵשׁ וּשְׁנַת עֶשְׂרִים כִּלְמַטָּה מִמֶּנָּה. הֵן. אִם עָשָׂה שְׁנַת שִׁשִּׁים כִּלְמַטָּה מִמֶּנָּה לְהַחֲמִיר, נַעֲשֶׂה שְׁנַת חָמֵשׁ וּשְׁנַת עֶשְׂרִים כִּלְמַטָּה מִמֶּנָּה לְהָקֵל. תַּלְמוּד לוֹמַר, שָׁנָה שָׁנָה, לִגְזֵרָה שָׁוָה. מַה שָּׁנָה הָאֲמוּרָה בִשְׁנַת שִׁשִּׁים, כִּלְמַטָּה מִמֶּנָּה, אַף שָׁנָה הָאֲמוּרָה בִשְׁנַת חָמֵשׁ וּשְׁנַת עֶשְׂרִים, כִּלְמַטָּה מִמֶּנָּה, בֵּין לְהָקֵל בֵּין לְהַחֲמִיר. רַבִּי אֶלְעָזָר אוֹמֵר, עַד שֶׁיִּהְיוּ יְתֵרוֹת עַל הַשָּׁנִים חֹדֶשׁ וְיוֹם אֶחָד:
“The [determination of] age is according to the subject of the vow" - how so? If a child evaluated an old man, he must pay the value of an old man; but, if an old man evaluated a child he must pay the value of a child. "The [gender for] the evaluations is according to the subject of the evaluation" - how so? If a man evaluated a woman, he must pay the value of a woman; but if a woman evaluated a man, she must pay the value of a man. “The [age for] evaluations [is determined] at the time of the evaluation" - how so? If he evaluated one who was less than five years of age, and [in the meantime] he became older than five years of age, or if [he evaluated one] who was less than twenty years of age and he became twenty years old, he must pay [only] according to the age at the time of the evaluation. The thirtieth day is considered to be under this age. The fifth year or twentieth year is considered to be under this age. For it says: “And if he is from sixty years old and upward” (Leviticus 27:7), thus we learn with regard to all others from what is said about sixty years: just as the sixtieth year is considered to be under this age, so also the fifth and twentieth years are under this age. [But] is that so? Just because [the Torah] accounts the sixtieth year to be under this age, thereby being more stringent, shall we account the fifth or the twentieth year to be under this age, in order to be lenient?! Scripture says, “year,” “year” as a <i>gezerah shavah</i> [a technique of halachic interpretation employing an established link between identical or nearly identical words]: just as with the sixtieth year the word “year” means that it is considered under this age, so the word “year” with the fifth and with the twentieth year are considered under this age, whether [this results in] being lenient or being stringent. Rabbi Elazar says: [this rule holds true] until they are a month and a day beyond the year.