Reference for Bava Kamma 93:7

משום דאמר ליה פרה מעברתא אזיקתך פרה מעברתא שיימנא לך

Said R. Aha the son of Raba to R. Ashi: If justice demands, why should not the defendant suffer? — Because he is entitled to say to him: 'Since it was a pregnant cow that I deprived you of, it is a pregnant cow which should be taken into valuation.'

Jastrow