Mar 3:4 Is it lawful to do good on the sabbath days, or to do evil? to save life, or to kill?
Is it allowed on the Sabbath days to do good or to injure? to keep a person alive or to slay?
This verse is identical to latter part of Luk 6:9 except for plural "sabbath days". The introduction is reflected in Mat 12:10.Whenever we see a verse where Christ uses a lot of unusual words, as he does here, one explanation is that he is repeated something those he is talking with have said. In this verse, we have some evidence of this. In Mat 12:10, this question was asked by his opponents of him.
Another interesting aspect of this verse is that Christ uses the verb forms of the Greek words that mean "good" and "evil". This is actually are not very common for him. The terms normally translated as "good" and "evil" in his words are more accurately translated as "beautiful" and "worthless."
"It is lawful" is a verb, which means "it is possible" and "it is allowed." It generally refers to something within someone's power, or, in this case with the negative, something outside of someone's power. This word does not, as it might seem, refer directly to Biblical law.
The word translated as the "on the Sabbath days" is the Greek version of the Hebrew word "shabbat" meaning "rest" or "day of rest".
The verb translated as "to do good" means "to do good", "to do well", "to act rightly," and "to exert a beneficial influence." It combines the verb meaning "to make" or "to perform" with the common Greek adjective meaning "useful", "worthwhile," and "of high quality. See this article on the real Greek meaning of the terms translated as "good" and "evil."
The verb translated as "to do evil" means "to do ill", "to play the knave," and "to do mischief," and "to injure." It combines the verb meaning "to make" or "to perform" with the common Greek adjective meaning many different forms of "bad," including "ugly", "low born", "craven," and "ill." In the NT, it is often translated as "evil." More about it in this article.
"To save" is the Greek word that means "to keep alive" when applied to people or "to keep safe" when applied to things. Christ uses it to mean "rescue" in most cases.
The word translated here as "life" is psyche, a common word in Greek meaning "life", "soul", "consciousness," and "a sense of self." Christ uses it to mean primary "spirit" or "mind." This is especially clear here where "mind" is contrasted with "body". This Greek word is our source of the English word "psyche."
"To kill" is translated from a Greek word that means "destroy" more than just "kill" because the base word means "slay." The Greek source has the sense of "kill off," that is, destroy in a more thorough way. When we talk about "destroying" someone, we use it to mean destroying their reputation, the strength of their spirit and ideas as well as physically killing them.
The "kill" also means "to destroy a reputation" and Christ often uses it when his position is challenges.
ψυχὴν (noun sg fem acc ) "Life" is psyche, which means "breath", "life", "self", "spirit," and "soul." It has the clear sense of the conscious self and is often translated as "life" in the Gospels. It is also used to describe "the spirit" of things. It is often translated as "soul."