Uhm... I think there should be a "not" in that particular commandment. "Shalt" is an older spelling of "shall", when English verbs were conjugated for each person like in other European languages. "I shall / I am / I may", "thou shalt / thou art / thou mayest" and so on. Adding "(es)t" was for the second person singular "thou". Nowadays, we use "you" and only conjugate for he/she/it. The use of "shall (shalt)" in this context is a mandate.

The Bible has been translated into English many times. The most famous translation is the 1611 "King James version." English speakers considered it "THE Bible" for a long time. The English in it is similar to the English of Shakespeare. It uses old-fashioned words and grammar which are hard for modern readers to understand. "Thou shalt not kill." is from Exodus 20:13 (l'Exode). It is one of the Ten Commandments (Décalogue). One French translation gives this verse as "Tu ne tueras point." It means "You shall not kill." Here, "shall" is a command, and "kill" means to kill another person. There is controversy over whether the accurate translation is "kill" or "murder." Murder means "killing ILLEGALLY." Killing in wartime is legal, so it is not murder. Capital punishment (peine de mort) is legal, so it is not murder. Some modern English translations say "You shall not kill." Others say "You shall not murder."

Well, "Shalt" is an out-dated version of "Shall", which was used for second-person singular 'Thou' (Thou means You). And "Thou Shalt" means "You Will/ Shall". So, your sentence, 'Thou shalt kill', means 'You will kill'. But as mentioned that it is from Bible, I'll say that you've read a misprinted Bible. The actual sentence is "Thou shalt not murder." meaning "You shall not murder."

You will/must/have to kill.