What is the ruling on someone who sacrifices a sheep and finds a lamb in its womb, and is it reprehensible to slaughter it if one knows it is pregnant?

Scholars differed regarding the ruling on sacrificing a pregnant animal. The majority of them hold it permissible. The Shāfi‘īs, however, believe it is not sufficient due to the corruption of its insides and the poor quality of its meat. It is preferable to avoid specifically selecting a pregnant animal, so as to avert disagreement. If one does select it, and it then becomes apparent that it is pregnant, sacrificing it is permissible. As for what is in its womb, its slaughter is the same as the slaughter of its mother, according to the majority of scholars, and this is the choice of Shaykh al-Islām Ibn Taymiyyah.