Lay your hand upon him- In order to show Israel that he is in place of him [Moshe], and he relied upon him.
ספרי במדבר
וסמכת את ידך עליו – א"ל תן תורגמן ליהושע, להיות שואל ודורש ומורה הוראות בחייך. כשתפטר מן העולם, לא יהי ישראל אומרים בחיי רבו לא הורה, ועכשיו הוא מורה.
Lay your hand upon him- He [God\ said to him [Moshe]: Appoint a speaker for Yehoshua, so he will ask, infer, and teach in your lifetime. When you leave this world, Israel shall not say: He did not rule during his teacher’s lifetime, and now he is ruling?!
וחד לא סמיך והא אמר רב יהודה אמר רב ברם זכור אותו האיש לטוב ורבי יהודה בן בבא שמו שאילמלא הוא נשתכחו דיני קנסות מישראל נשתכחו נגרוסינהו אלא
בטלו דיני קנסות מישראל שפעם אחת גזרה מלכות הרשעה גזירה על ישראל שכל הסומך יהרג וכל הנסמך יהרג ועיר שסומכין בה תיחרב ותחומין שסומכין בהן יעקרו מה עשה יהודה בן בבא הלך וישב לו בין שני הרים גדולים ובין שתי עיירות גדולות ובין שני תחומי שבת בין אושא לשפרעם וסמך שם חמשה זקנים ואלו הן ר"מ ור' יהודה ור' שמעון ור' יוסי ור' אלעזר בן שמוע רב אויא מוסיף אף ר' נחמיה כיון שהכירו אויביהם בהן אמר להן בניי רוצו אמרו לו רבי מה תהא עליך אמר להן הריני מוטל לפניהם כאבן שאין לה הופכים אמרו לא זזו משם עד שנעצו בו שלש מאות לונביאות של ברזל ועשאוהו ככברה.
the laws of fines would have ceased to be implemented from among the Jewish people, as they would not have been able to adjudicate cases involving these laws due to a lack of ordained judges. This is because at one time the wicked kingdom of Rome issued decrees of religious persecution against the Jewish people with the aim of abolishing the chain of ordination and the authority of the Sages. They said that anyone who ordains judges will be killed, and anyone who is ordained will be killed, and the city in which they ordain the judges will be destroyed, and the signs identifying the boundaries of the city in which they ordain judges will be uprooted. These measures were intended to discourage the Sages from performing or receiving ordination due to fear for the welfare of the local population. What did Rabbi Yehuda ben Bava do? He went and sat between two large mountains, between two large cities, and between two Shabbat boundaries: Between Usha and Shefaram, i.e., in a desolate place that was not associated with any particular city so that he not endanger anyone not directly involved, and there he ordained five elders. And they were: Rabbi Meir, and Rabbi Yehuda, and Rabbi Shimon, and Rabbi Yosei, and Rabbi Elazar ben Shammua. Rav Avya adds that Rabbi Neḥemya was also among those ordained. This incident indicates that ordination can be performed by a single Sage. When their enemies discovered them, Rabbi Yehuda ben Bava said to the newly ordained Sages: My sons, run for your lives. They said to him: My teacher, what will be with you? Rabbi Yehuda ben Bava was elderly and unable to run. He said to them: In any case, I am cast before them like a stone that cannot be overturned; even if you attempt to assist me I will not be able to escape due to my frailty, but if you do not escape without me you will also be killed. People say about this incident: The Roman soldiers did not move from there until they had inserted three hundred iron spears [lunkhiyot] into him, making him appear like a sieve pierced with many holes.
Torah Musings- 11/29/13
According to many, the chain of semikhah was finally broken around 360 CE, when Hillel II dissolved the Sanhedrin and fixed the Jewish calendar.6 There is evidence, however, which suggests that semikhah continued to be conferred in the Land of Israel for centuries.7
See also J. Newman, Semikha (Manchester: Manchester University Press, 1950), pp. 144-154, who suggests that semikhah continued until the death of R. Daniel ben Azaryah Gaon in 1062, and Yehuda ben Barzillai of Barcelona, Sefer ha-Shtarot, p. 132, where it is implied that even in his days (ca. 11th-12th C.) there was some form of semikhah in the Land of Israel.
ענין הסמיכות שנהגו בזמן הזה כדי שידעו כל העם שהגיע להוראה ומה שמורה הוא ברשות רבו הסומכו
The essence of semikhah which is practiced in these days is for the people to know that this individual is capable of ruling, and that his rulings are given with permission of his teacher who ordained him.
(יא) הֲרֵי שֶׁלֹּא הָיָה בְּאֶרֶץ יִשְׂרָאֵל אֶלָּא סוֹמֵךְ אֶחָד מוֹשִׁיב שְׁנַיִם בְּצִדּוֹ וְסוֹמֵךְ שִׁבְעִים כְּאֶחָד אוֹ זֶה אַחַר זֶה וְאַחַר כָּךְ יַעֲשֶׂה הוּא וְהַשִּׁבְעִים בֵּית דִּין הַגָּדוֹל וְיִסְמְכוּ בָּתֵּי דִּינִין אֲחֵרִים. נִרְאִין לִי הַדְּבָרִים שֶׁאִם הִסְכִּימוּ כָּל הַחֲכָמִים שֶׁבְּאֶרֶץ יִשְׂרָאֵל לְמַנּוֹת דַּיָּנִים וְלִסְמֹךְ אוֹתָם הֲרֵי אֵלּוּ סְמוּכִים וְיֵשׁ לָהֶן לָדוּן דִּינֵי קְנָסוֹת וְיֵשׁ לָהֶן לִסְמֹךְ לַאֲחֵרִים. אִם כֵּן לָמָּה הָיוּ הַחֲכָמִים מִצְטַעֲרִין עַל הַסְּמִיכָה כְּדֵי שֶׁלֹּא יִבָּטְלוּ דִּינֵי קְנָסוֹת מִיִּשְׂרָאֵל. לְפִי שֶׁיִּשְׂרָאֵל מְפֻזָּרִין וְאִי אֶפְשָׁר שֶׁיַּסְכִּימוּ כֻּלָּן. וְאִם הָיָה שָׁם סָמוּךְ מִפִּי סָמוּךְ אֵינוֹ צָרִיךְ דַּעַת כֻּלָּן אֶלָּא דָּן דִּינֵי קְנָסוֹת לַכּל שֶׁהֲרֵי נִסְמַךְ מִפִּי בֵּית דִּין. וְהַדָּבָר צָרִיךְ הֶכְרֵעַ:
It appears to me that if all the all the wise men in Eretz Yisrael agree to appoint judges and convey semichah upon them, the semichah is binding and these judges may adjudicate cases involving financial penalties and convey semichah upon others.
If so, why did the Sages suffer anguish over the institution of semichah, so that the judgment of cases involving financial penalties would not be nullified among the Jewish people? Because the Jewish people were dispersed, and it is impossible that all could agree. If, by contrast, there was a person who had received semichah from a person who had received semichah, he does not require the consent of all others. Instead, he may adjudicate cases involving financial penalties for everyone, for he received semichah from a court.
The question whether semichah can be renewed requires resolution.