If I understand your question correctly, you may be asking why a Christian would ever be directed to “have” his faith “to himself before God”. However, I do not believe that a Christian is ever to keep silent about the beautiful Gospel of the Lord Jesus Christ, salvation by Grace through faith in the Lord Jesus Christ alone (Ephesians 2:8,9; Titus 3:5). Much to the contrary, we are asked to share the Gospel widely and with boldness. In fact, from the context, this chapter has to do with the acceptance of or conduct towards weaker or more immature Christians by more mature Christians.  We find here principles for how we use our liberty in certain matters that might be “morally neutral”. All people, who have been saved by the Grace of our Lord Jesus Christ through faith in His death and resurrection are Christians, and in this chapter, we are speaking of Christians.

The crux of this chapter is that we should always act, despite our Christian liberty, to edify rather than to stumble and thus harm the weaker believer. William MacDonald, in his commentary on this chapter identifies the thrust of the chapter as follows: “Romans 14:1-15:13 deals with important principles to guide God’s people in dealing with matters of secondary importance”. I think we need to observe here that many of the early Christians were from a Jewish background. These matters “of secondary importance”, as MacDonald calls them, generally have to do with matters of individual conscience, such as refusing pork or other forbidden meats cited in the Law of Moses or forbidding to work on the Sabbath (Saturdays). The sacrifices of the Old Testament all pointed to Christ, and the ceremonial laws all had their place in setting Israel apart as God’s people. But, after the cross of Christ, the way to salvation was now to be based wholly and alone on faith in the finished work of Christ Jesus on the cross, and Jew and Gentiles alike were to come to God on this same ground, being one body in Christ. As we see in 1 Timothy 4:4-5, Christians today no longer are required to refuse certain meats as in the Old Testament.  “For every creature of God is good, and nothing to be refused, if it be received with thanksgiving: For it is sanctified by the word of God and prayer”.

But as we see outlined in Romans 14:1-3, some of the more “immature” Christians of Jewish backgrounds continued to have a conscience about eating things forbidden in the OT, and some of the Christians who better understood their NT liberty were standing in personal judgment on these folks. We see similar issues with the desire of the Jewish Christians feeling the need to observe the Sabbath, or those who wanted to observe other certain days seen as sacred (see Romans 14:5,6). Christians  in the NT are not asked to keep a “Sabbath”; rather, we generally gather to remember the Lord and to worship Him on the first day of the week, Sunday, because the Lord Jesus rose from the dead on that day, and the Lord appeared to His disciples in the upper room on that day.  Meeting on the first day of the week, Sunday, which we call “the Lord’s day, quickly became the practice of Christians in the early church. And now, we come to the verse you cited. We read in Romans 14:21-23: “It is good neither to eat flesh, nor to drink wine, nor any thing whereby thy brother stumbleth, or is offended, or is made weak. Hast thou faith? have it to thyself before God. Happy is he that condemneth not himself in that thing which he alloweth. And he that doubteth is damned if he eat, because he eateth not of faith: for whatsoever is not of faith is sin”.

My dear friend, I want to stress again that the matters listed above do not impact at all on a person’s salvation, so long as a person has trusted in the finished work of Christ on the cross, and has trusted in Him alone for salvation, and not on works of the law. The problem seemed to be that the more mature Christians were judging the less mature Christians who were acting on the basis of their own conscience.  This was discouraging or even stumbling the less mature Christians (Romans 14:4-12).  In verse 10, we see that judgment as to the service of a Christian is a matter for the Lord, and not for other Christians, to deal with at the Judgment Seat of Christ.

So, how should the mature Christian who is fully aware of his liberty treat those with a lesser understanding? Verses 13-21 says that though a mature Christian may realize that he can eat any type of meats or drink a glass of wine with a meal, if a younger Christian has a conscience about these things, we should treat them with love and not put them in the situation of having to violate their conscience. I may understand that Christians have liberty to eat pork, but if a weaker Christian would be stumbled and thrown into a personal crisis about this, I simply will have my faith about this matter, but when with them, I would certainly not serve them pork. I should not flaunt my liberty if it hurts another. Verse 21 reads: “It is good neither to eat flesh, nor to drink wine, nor any thing whereby thy brother stumbleth, or is offended, or is made weak”. MacDonald sums it up in his Bible Commentary as follows: “It is good to walk in the full enjoyment of one’s Christian liberty, not being fettered by unwarranted scruples. But it is better to forego one’s legitimate rights than have to condemn oneself for offending others. One who avoids stumbling others is the happy person.”  (SF)  (517.3)