Rabban Gamliel sent [a message] to him, “I decree upon you that you come to me with your staff and your money on the day that Yom Kippur will fall according to your reckoning.”  R’ Akiva went and found him troubled, [so] he said to him, “I can elucidate that whatever Rabban Gamliel did is [validly] done, for it says: These are the holidays of HASHEM, holy convocations, that you shall declare them —- whether [declared] in their [expected] time or not in their [expected] time, I have no holidays but these.”  He came to R’ Dosa ben Harkinas, who said to him, “If we come to reconsider [the decisions of] Rabban Gamliel’s beis din, then we must reconsider [the decisions of] every beis din that arose from the days of Moses until now, as it says: There went up Moses and Aaron, Nadav and Avihu, and seventy of the elders of Israel. Why are the names of the elders not expressly mentioned? Only to each [us] that every three [people] who arose as a beis din for Israel are considered like the beis din of Moses.”  [Then] he took his staff and his money in his hand and went to Yavneh to Rabban Gamliel on the day that Yom Kippur fell according to his reckoning.  Rabban Gamliel stood up and kissed him on his head, and said to him, “Come in peace, my master and my disciple! My master in wisdom, and my disciple in that you accepted my words.”

If the beis din and all of Israel saw [the moon], or if the witnesses were interrogated, but they did not manage to say, “It is sanctified,” before it grew dark —- it is full.  If only beis din saw it, two [of them] should stand and testify before the others, and they should say, “It is sanctified, it is sanctified!”  If three saw it and they constitute a beis din, [then] two should stand up and set some of their colleagues beside the single one and testify before them, and say, “It is sanctified, it is sanctified!” For an individual is not trusted alone.