score:5
The phrasing depends on which nuance you would like to communicate:
"for Christ": align your will with Christ's agenda and dedicate your effort for Jesus
"for Christ's sake" or "for the sake of the gospel" is quite common in the Bible (see Paul Chernoch's answer).
The meaning is be similar to the old British military slogan "for Queen and country". Another famous slogan is "for the greater glory of God" (Ad maiorem Dei gloriam).
Unfortunately "for Christ's sake" has been debased into blasphemous speech outside church nowadays.
If this is the nuance you want, you can use "for the sake of Christ" or "truly for Christ".
"in Christ": you are acting as a member of the body of believers organically united to Christ
See the CS Lewis Institute issue of Knowing & Doing article "In Christ" - The Meaning and Implications of the Gospel of Jesus Christ exploring 3 implications of being "in Christ":
Thus, this construction emphasizes the collective identity aspect to communicate that you act as a part of a church, doing your part to achieve a goal larger than yourself. This collective feeds on Christ and operates on an ideal which brings the collective to ever greater holiness.
We can see how in a healthy secular collective (like a society, political party, or military) the same principles apply: unity of purpose drawing on a source of energy (such as love for music, justice, country, etc), and ever-reforming and rejuvenating itself.
If this is the nuance you want, you can use "truly in Christ".
"stand for Christ": means acting or behaving according to Christian standard despite opposition/persecution
"in Jesus's name": means you are acting in the authority of Jesus
"through Christ": this means you are relying on the power of Christ
This is frequently conveyed by Phil 4:13: What Does it Mean, 'I can Do All Things through Christ'?.
If this is the nuance you want, you can use something like "through Christ"
"in the person of Christ": you are acting as though Jesus himself is in you
This is based on 2 Cor 2:10 and Luke 10:16.
This means every visible expression and everything you say and do will appear as though Christ acts through you. This nuance should be reserved if you are prepared to be Christ's witness in every aspect of your life knowing that others are watching.
Roman Catholic priests are very conscious in acting in persona Christi especially in performing sacraments while being robed with appropriate vestments, doing and saying the prescribed gestures and words.
If this is the nuance you want, you can use something like "being Christ"
Upvote:4
In the New Testament, "in Christ" is the most common usage, demonstrating membership in the body of Christ and full agreement with his will.
"For Christ" is also used to indicate loyalty and devotion. Here are verses where it is used, sometimes directly as "for Christ", sometimes in the construction "for the sake of Christ", and sometimes in rearranged phrases that separate "for" and "Christ". I exclude verses where "for" means "because".
Philippians has the most usages:
As a result, it has become clear throughout the whole palace guard and to everyone else that I am in chains for Christ. (1:13)
For it has been granted to you on behalf of Christ not only to believe in him, but also to suffer for him (1:29)
For everyone looks out for their own interests, not those of Jesus Christ. (2:21)
because he almost died for the work of Christ. He risked his life to make up for the help you yourselves could not give me. (2:30)
But whatever were gains to me I now consider loss for the sake of Christ. (3:7)
What is more, I consider everything a loss because of the surpassing worth of knowing Christ Jesus my Lord, for whose sake I have lost all things. I consider them garbage, that I may gain Christ (3:8)
Despite "for Christ" being the less common, the use of the construction "for the sake of Christ" in Philippians is so powerful (and a memorable verse) that I would not discourage its use.
The concept of being "in Christ" was not easy for me to grasp as a new believer. The meaning of it is richer than "for Christ", but to a general audience, "for Christ" will be more understandable.
The one caveat is that the goal of being "in" Christ is to surrender to his will, whereas being "for" Christ connotes exercising your independent will in alignment with his. The focus is more on you, less on him.