Yoreh Deah Siman 16 Seif 3

 

ג עָבָר וְשָׁחַט אוֹתוֹ וְאֶת בְּנוֹ בְּיוֹם א’, מֻתָּר לְאָכְלָם; וְיֵשׁ מִי שֶׁאוֹסֵר בּוֹ בַּיּוֹם לֶאֱכֹל הָאַחֲרוֹן.

 

Seif 3

If one violates this prohibition and slaughters a mother and its offspring on the same day, it is allowed to eat of it, There are those who do not allow it. (to eat the second one slaughtered on the same day).