Instructions for the strong
Do not by your eating destroy your brother for whom Christ died. 16 Do not allow what you consider good to be spoken of as evil. 17 For the kingdom of God is not a matter of eating and drinking, but of righteousness, peace, and joy in the Holy Spirit, 18 because anyone who serves Christ in this way is pleasing to God and approved by men.
Paul seems concerned that people are misunderstanding what is good. They are misunderstanding the kingdom of God. They are having trouble with the basics. That is why they are struggling with specifics. Serve Christ! That is the bottom line. Use your freedom in Christ to serve your neighbor, and in that way you will serve Christ.
Matthew Henry, on the kingdom of God:
First, It is not meat and drink: it does not consist either in using or in abstaining from such and such meats and drinks. Christianity gives no rule in that case, either in one way or another. The Jewish religion consisted much in meats and drinks (Heb. ix. 10), abstaining from some meats religiously (Lev. xi. 2), eating other meats religiously, as in several of the sacrifices, part of which were to be eaten before the Lord: but all those appointments are now abolished and are no more, Col. ii. 21, 22. The matter is left at large.
Every creature of God is good, 1 Tim. iv. 4. So, as to other things, it is neither circumcision nor uncircumcision (Gal. v. 6; vi. 15; 1 Cor. vii. 19), it is not being of this party and persuasion, of this or the other opinion in minor things, that will recommend us to God.
It will not be asked at the great day, "Who ate flesh, and who ate herbs?" "Who kept holy days, and who did not?" [...] But it will be asked, "Who feared God and worked righteousness, and who did not?" Nothing more destructive to true Christianity than placing it in modes, and forms, and circumstantials, which eat out the essentials.
Secondly, It is righteousness, and peace, and joy in the Holy Ghost. These are some of the essentials of Christianity, things in which all the people of God are agreed, in the pursuit of which we must spend our zeal, and which we must mind with an excelling care. Righteousness, peace, and joy, are very comprehensive words; and each of them includes much, both of the foundation and the superstructure of religion.
Might I limit the sense of them, it should be thus.
As to God, our great concern is righteousness--to appear before him justified by the merit of Christ's death, sanctified by the Spirit of his grace; for the righteous Lord loveth righteousness.
As to our brethren, it is peace--to live in peace and love, and charity with them, following peace with all men: Christ came into the world to be the great peace-maker.
As to ourselves, it is joy in the Holy Ghost--that spiritual joy which is wrought by the blessed Spirit in the hearts of believers, which respects God as their reconciled Father and heaven as their expected home. Next to our compliance with God, the life of religion consists in our complacency in him; to delight ourselves always in the Lord. Surely we serve a good Master, who makes peace and joy so essential to our religion. Then and then only we may expect peace and joy in the Holy Ghost when the foundation is laid in righteousness, Isa. xxxii. 17.
Thirdly, It is in these things to serve Christ (v. 18), to do all this out of respect to Christ himself as our Master, to his will as our rule and to his glory as our end. That which puts an acceptableness upon all our good duties is a regard to Christ in the doing of them. We are to serve his interests and designs in the world, which are in the first place to reconcile us one to another. What is Christianity but the serving of Christ? And we may well afford to serve him who for us and for our salvation took upon him the form of a servant.