Verses 20 and 21 deal with a single act of violence against slaves. When is literally “And if [ki]” as in verse 18. When a man strikes … with a rod refers to “a slaveowner” (New Revised Standard Version) who “beats … with a stick.” This is the same verb used in verses 12, 15, and 18. The word for rod may mean a stick, a staff, or a club, depending on the context. Verse 19 uses a different word, but both words are translated the same way by Revised Standard Version in Psa 23.4. Moses’ “rod” in 4.2 is yet another Hebrew word.

His slave, male or female is literally “his male slave or his female slave,” using the same words that are used in verses 1 and 7. (See the comment there.) And the slave dies is literally “and he dies.” Under his hand is quite literal and probably means, as Good News Translation expresses it idiomatically, “on the spot,” or “there and then” (New Jewish Publication Society’s Tanakh), or “immediately” (New Revised Standard Version). But New International Version‘s “as a direct result” is also possible. It must be clear, however, that “the slave dies from the beating” (Durham).

He shall be punished is literally “punished he shall be punished,” using the same emphatic form as “dying he shall die” in verse 12. The basic meaning of the verb is to take revenge, so Translator’s Old Testament has “the death shall be avenged.” But the kind of punishment is not indicated, and it does not say “dying he shall die.” Most scholars conclude, therefore, that it probably refers to a less serious punishment to be determined by a judge. In languages that do not use the passive voice, one may say, for example, “he will receive punishment” or “they must punish him.”

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .