What is the Christian life?

TL;DR:

The Christian life is a response to God's grace that is rooted in faith, expressed through love, and lived in obedience to Christ. Though the Christian life involves sacrifice and perseverance, it is marked by purpose, joy, and the hope of eternal life with God.

what does the bible say?

We receive our new identity as God’s children by grace through faith in Jesus Christ (Ephesians 2:8–9). Understanding our new identity is foundational to living out our Christian life from a biblical perspective. Extending Christ-centered love to God and to those around us are the most important commandments we are to fulfill in our lives (Mark 12:30–31). This love can be shown in many ways, such as sharing the gospel (Matthew 28:18–20) or serving those in need (James 1:27). However, there are other things that are involved in our faith walk, like living by faith (Galatians 3:11), persevering through “various kinds” of trials (James 1:2–4), and sacrificing ourselves and rejecting what the world has to offer in favor of allegiance to Jesus Christ (Ephesians 2:8–9). Lastly, we should “honor Christ the Lord as holy” in our hearts and be prepared to make a defense to those who ask about our faith in Jesus Christ, demonstrating “gentleness and respect” while doing so (1 Peter 3:15). Although the Chrisian life has its sacrifices (Romans 12:1–2), we can find comfort in knowing that the trials and pain we endure in this life will soon pass away when we enter into eternity with God (Revelation 21:4).

from the old testament

The Old Testament doesn't use the term "Christian life" since it predates Jesus Christ, but it lays a foundation for what the Christian life would later become. The core principles of the Christian life—faith, obedience, love, justice, humility, and relationship with God—are deeply rooted in the Old Testament.
Habakkuk 2:4 tells us that faith in God’s character and promises are central to our relationship with God. This verse is later quoted in the New Testament to describe life in Christ (Romans 1:17).
Deuteronomy 6:5 sums up the Law as wholeheartedly living for God. This
is the foundation of both Old and New Testament teaching on how we are to live.
Doing justice, loving mercy, and walking humbly is what a life shaped by God’s character and priorities looks like (Micah 6:8).
God's people were to live differently, set apart to reflect His holiness (Leviticus 20:26).

from the new testament

In Matthew 28:18–20, Jesus tells His disciples to “make disciples of all nations.” We, as Christians, can also engage in evangelism as a way to show love to those who need the gospel.
The Christian life should be centered on love. In Mark 12:30–31, Jesus says, “‘And you shall love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.’ The second is this: ‘You shall love your neighbor as yourself.’ There is no other commandment greater than these."
A Christian's life is one devoted to living for God. Instead of being changed by the world, the Christian is changed by Christ and then changes the world. Romans 12:1–2 shows how this process looks: "I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect."
Galatians 3:11 teaches that the Christian life is to be lived by faith: "Now it is evident that no one is justified before God by the law, for 'The righteous shall live by faith.’” Christians seek to live out the teachings of Jesus and of Scripture, and they do so by faith based on love for God and others. A Christian lives for Christ because of God's love, not to earn it.
The distinguishing mark of the Christian life is to live by faith. A person becomes a Christian by grace through faith in Jesus Christ. Ephesians 2:8–9 teaches, "For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast." This faith in Jesus Christ changes one's life, beginning the process of a life of faith.
The Christian life includes much endurance or perseverance. James 1:2–4 notes, "Count it all joy, my brothers, when you meet trials of various kinds, for you know that the testing of your faith produces steadfastness. And let steadfastness have its full effect, that you may be perfect and complete, lacking in nothing." It is much easier to begin well than to end well in the Christian life. God calls us to faithfully endure life's challenges and even to rejoice during them, as they help increase our endurance in living for Christ.
Jesus came to serve others, and He calls us to do the same. This involves loving our neighbor as we love ourselves and helping those in need (James 1:27).
In 1 Peter 3:15, Peter tells his Christian audience: “but in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect." Christians today should do this, too.
If we are struggling in the Christian life, we can be look forward to and be encouraged by Revelation 21:4: “He will wipe away every tear from their eyes, and death shall be no more, neither shall there be mourning, nor crying, nor pain anymore, for the former things have passed away."

implications for today

The Christian life is not easy. However, it is the source of abundant life (John 10:10) as well as eternal life (John 3:16). It is one of faith, love, and hope (1 Corinthians 13:12–13) that reflects the life and teachings of Jesus Christ. Although our Christian walk is likely to be one that involves sacrifice (Romans 12:1–2) and trials (James 1:2), we can be assured “that the testing of [our] faith produces steadfastness” (James 1:3) and that “for those who love God all things work together for good, for those who are called according to his purpose” (Romans 8:28). It is Jesus who promises to empower us for service, help us in times of temptation, and ultimately live with His children for all eternity. If we are needing wisdom in our walk with God, we can look to the Bible, other believers, and ultimately God for help: “If any of you lacks wisdom, let him ask God, who gives generously to all without reproach, and it will be given him” (James 1:5).

understand

The Christian life begins by grace through faith in Jesus Christ, giving us a new identity as children of God.
The Christian life is lived out through love, obedience, service, and perseverance.
The Christian life reflects Christ’s character.

reflect

In what ways are you currently living by faith, even when it's hard to see the outcome?
How are you expressing love for God and others in your daily routines and relationships?
When trials come, how does your Christian life impact your perspective and your actions?

engage

What does it look like for us to live lives that reflect Christ’s love and holiness in today’s world?
How can we support one another in persevering through trials as we walk out the Christian life?
How can we clearly and compassionately share with others the purpose behind living a life of obedience and holiness that God calls us to?