What does the Bible teach about a Christian's responsibility?

TL;DR:

A Christian’s responsibility is to love the Lord and to love others. This is the foundation of every duty in life.

The Bible indicates that followers of the Lord have a responsibility to love the Lord and to love others. Many different responsibilities fall under these two key commands. In the Old Testament, God gave His people, the Israelites, the Mosaic Law, which pointed to His holiness and the need for those who followed Him to be holy. The Law was fulfilled in Jesus Christ. Jesus reiterated the two foundational responsibilities of His followers to love God and love others. Sharing the gospel (Matthew 28:18–20), praying (Philippians 4:4–7), doing good to others (James 1:27; 2:14–16), and conducting our lives as a living testimony to Christ (1 Corinthians 10:31; Colossians 3:23–24) fall under those two commands. Essentially, our responsibility is to show our love of God and of others, living our lives with an eternal perspective (Colossians 3:2–4).

from the old testament

“Christians” weren't a named group until the New Testament era, but followers of the Lord in the Old Testament were called to love God with their whole being (Deuteronomy 6:5) and to love others (Leviticus 19:18). In the gospels, Jesus mentioned that these commands are the heart of the entire Law (cf. John 14:15).

from the new testament

The command to love God and love others is the foundation for New Testament commands as well (Matthew 22:37–40). Loving the Lord involves doing what He has commanded us (John 14:15).
Jesus calls us to disciple others to believe in Him: “Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, to the end of the age” (Matthew 28:19–20).
As Christians, we’re responsible for leading lives that honor God in all that we do (1 Corinthians 10:31; Colossians 3:23–24).
Showing love toward others isn’t just saying nice things to them; it’s doing things for others to care for them (James 2:14–16).

implications for today

If you’ve ever played Jenga, you know the goal is to strategically remove and re-stack blocks from a tower of blocks without making the entire structure fall. Sometimes, life feels like a Jenga game: We have a tower of responsibilities, and we try to move them around to see where else we can fit them. Sometimes, our tower falls.

A Christian’s responsibilities, though, can’t be separated into blocks. Instead, all parts of our lives must be permeated by the chief responsibility of glorifying God (1 Corinthians 10:31). Christians’ responsibilities toward family should reflect God’s will for the family unit (Ephesians 5–6). At our jobs, we’re to “work heartily as for the Lord” (Colossians 3:23). Our entertainment options should not be those that promote ungodly behavior (Ephesians 5:4).

In short, for Christians, loving God and loving others is the entire “tower.” Our responsibility as Christians is to walk in the way of the Lord.

understand

A Christian's core responsibility is to love God and love others.
Living out this love involves action, not just belief.
Every part of a Christian’s life should reflect God's will.

reflect

How does your daily routine reflect your love for God and others, and where might your priorities need realignment?
How are you actively living out your faith?
What influences in your life—work, family, entertainment—either support or distract you from your responsibility to glorify God?

engage

How can we help each other keep the love of God and others at the center of all our responsibilities?
What challenges do Christians face when trying to live every part of life—public and private—in a way that honors God?
How does understanding our responsibilities in light of eternity shape the way we approach everyday decisions?