אָב וּבְנוֹ שֶׁרָאוּ אֶת הַחֹדֶשׁ, יֵלְכוּ. לֹא שֶׁמִּצְטָרְפִין זֶה עִם זֶה, אֶלָּא שֶׁאִם יִפָּסֵל אֶחָד מֵהֶן, יִצְטָרֵף הַשֵּׁנִי עִם אַחֵר. רַבִּי שִׁמְעוֹן אוֹמֵר, אָב וּבְנוֹ וְכָל הַקְּרוֹבִין, כְּשֵׁרִין לְעֵדוּת הַחֹדֶשׁ. אָמַר רַבִּי יוֹסֵי, מַעֲשֶׂה בְטוֹבִיָּה הָרוֹפֵא, שֶׁרָאָה אֶת הַחֹדֶשׁ בִּירוּשָׁלַיִם, הוּא וּבְנוֹ וְעַבְדּוֹ מְשֻׁחְרָר, וְקִבְּלוּ הַכֹּהֲנִים אוֹתוֹ וְאֶת בְּנוֹ, וּפָסְלוּ אֶת עַבְדּוֹ. וּכְשֶׁבָּאוּ לִפְנֵי בֵית דִּין, קִבְּלוּ אוֹתוֹ וְאֶת עַבְדּוֹ, וּפָסְלוּ אֶת בְּנוֹ:

If a father and son saw the new moon, they must both go to the court; not that they may be combined as witnesses, but rather that in the event that one of them be declared unfit, the other may join with another witness. Said Rabbi Shimon, "A father and his son, and all relatives, are fit to join together to give testimony about the new moon." Said Rabbi Yosei, "It once happened that Toviah the physician, his son, and his freed slave saw the new moon in Jerusalem, and the Kohanim accepted him and his son as witnesses together, but declared his slave unfit; but when they came to the court, they accepted him and his slave as witnesses, but declared his son unfit."