Rosh Hashanah 3:6
Rosh Hashanah3: 6
שׁוֹפָר שֶׁנִּסְדַּק וְדִבְּקוֹ, פָּסוּל. דִּבֵּק שִׁבְרֵי שׁוֹפָרוֹת, פָּסוּל. נִקַּב וּסְתָמוֹ: אִם מְעַכֵּב אֶת הַתְּקִיעָה, פָּסוּל; וְאִם לָאו, כָּשֵׁר.
Ashofar that was split and he glued it together, it is invalid. If he glued together broken pieces of a shofar, it is invalid. If there is a hole [in the shofar] and he sealed it: if it hinders the blowing, it is invalid; and if not, it is valid.