(Exodus 21:37) introduces the severe penalty for livestock theft: "If a man steal an ox or a lamb and slaughter it or sell it, he shall pay five oxen for the ox and four sheep for the lamb." The four-and-five payment is one of the harshest financial penalties in the Torah. But why is it necessary?
The Mekhilta explains that both the slaughterer and the seller of stolen livestock were already included in the general rule of (Exodus 22:6): "If the thief is found, he shall pay double." Any thief caught with stolen property pays twice its value. Slaughtering or selling are just two things a thief might do with what he stole.
The Torah deliberately removed these two cases from the general category and placed them in their own section with a harsher penalty. A thief who steals and keeps the animal pays double. A thief who steals and then slaughters or sells it pays four or five times the value. The act of destruction or disposal aggravates the crime.
Why the escalation? Slaughtering destroys the evidence and makes the animal irrecoverable. Selling transfers it beyond the owner's reach. Both actions represent a deeper commitment to the theft — the thief is not merely holding stolen property but has taken irreversible steps to profit from it. The Torah treats the permanence of the theft as an aggravating factor deserving a steeper penalty.