Ethics consists of three elements: an authoritative rule, a desired outcome, and a manner of life or habit.
Each of these elements is present in 1 Thessalonians 4:1–2.
As for other matters, brothers and sisters, we instructed you how to live in order to please God, as in fact you are living. Now we ask you and urge you in the Lord Jesus to do this more and more. For you know what instructions we gave you by the authority of the Lord Jesus.
The authoritative rule is the easiest element of ethics to understand. Paul, Silas, and Timothy wrote, “we instructed you how to live.” That’s what rules do: they show us how to act and how not to act. In Scripture, authoritative rules include the Great Commandment (Matt. 22:37–40, cf. Deut. 6:5, Lev. 19:18), the Ten Commandments (Ex. 20:1–17, Deut. 5:6–21), the Antitheses (Matt. 5:21–48), the Golden Rule (Matt. 7:12), and the Law of Love (John 15:12, 17). These rules can be stated positively (“Love your neighbor”) or negatively (“You shall not give false testimony against your neighbor”). These are not different rules, but the same rule, applying love to different cases. Regarding the Great Commandment, Jesus says, “All the Law and the Prophets hang on these two commandments” (Matt. 22:40). These rules are authoritative because they flow out of “the authority of the Lord Jesus,” who himself is the point of “the Law of Moses, the Prophets, and the Psalms” (Luke 24:44).
The desired outcome of ethics is what Martin Luther King Jr. called “the beloved community,” a community in which neighbors love one another and all love God, who made them. The rules demarcate the boundary between behaviors that foster the beloved community and those that hinder it. King, for example, critiqued Jim Crow segregation because it treated neighbors unequally, based solely on the color of their skin. A beloved community cannot be created when its white citizens were allowed to murder, rape, steal from, and lie against their black neighbors with impunity. Of course, a community is more than mere rule-keeping, but we need to see the connection between rules and outcomes. For the missionaries, the desired outcome was “to please God,” and God is pleased when we love one another.
The manner of life is that habit that is necessary for us to create the beloved community. In his Antitheses, Jesus went beyond the external observance of rules to the internal character that drives behavior. It is relatively easy never to kill someone. Not being angry with them is much harder (Matt. 5:21–22). To not be angry with others, we must develop the habits of reconciliation (5:23–24) and settling matters quickly (5:25–26), rather than denying forgiveness and nursing grudges. We develop such habits through practice: “do this more and more.” You have heard the saying, “Practice makes perfect”? The truth is, whatever we do habitually, “Practice makes permanent.”
For the Christian, then, love is our authoritative rule, the beloved community our desired outcome, and resolving conflicts our manner of life.