Reference for Keritot 15:45

כיון דלאו בזמן חיובא קחזי ליה לא תצטרף קמ"ל:

<big><b>GEMARA: </b></big>Our Rabbis taught: If she had five certain births and five doubtful ones, or five certain issues and five doubtful ones, she brings two pairs of birds, one for the certain and one for the doubtful cases.

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