Rashi on Exodus 21:32/רש"י על שמות כ״א:ל״ב

1אם עבד או אמה IF [AN OX SHALL THRUST] A MANSERVANT OR A MAIDSERVANT — Canaanitish servants (Mekhilta).

2שלשים שקלים יתן HE SHALL GIVE THIRTY SHEKELS — This is the enactment of Scripture (and no reason is given) — the indemnity shall be thirty shekels whether the slave was worth a thousand zuz or was worth no more than one denar. A shekel weighs four gold coins, making half an ounce according to the correct weight of Cologne.