There is the question of which commandments we are to obey in 1 John 5:3 and in 2 John 1:6, as the result of loving the Lord our God with all of our heart, soul, mind, and strength.
Do we obey all of the commandments in the Old Testament? Matthew 5:17-20, Hebrews 8:10, Hebrews 10:16, Jeremiah 31:33, Romans 8:4-7 would seem to tell us so.
We will be called great in the kingdom if we obey and teach the least of these God's commandments. In context (in Matthew 5:17-20) Jesus is talking about the Old Testament law.
But concerning this, it seems that Jesus Himself taught that the Old Testament commandments concerning food laws and the sabbath are now invalid. For He Himself broke the sabbath according to John's testimony (John 5:18); and He also proclaimed on more than one occasion that all foods are now clean (Mark 7:14-19, Luke 11:41, Romans 14:14).
Yet the law is a schoolmaster to lead men to Christ (Galatians 3:24-25); it shows men their sin (Romans 3:20) and brings them to the place of being converted (Psalms 19:7). I don't think that this is talking about the law as it is now that it has been changed for the believer (Hebrews 7:12).
The law has only been changed in that it is no longer given to us as a set of do's and don'ts, but as a list of virtues to be exemplified and vices to be avoided (Galatians 5:16-24). We are told not to walk according to the flesh and that we will reap what we sow, even as believers (Galatians 6:7-8).
And also, the Old Testament sacrifices are no longer needed, because Christ dying on the Cross is the fulfillment of them.
So then, concerning food laws and sabbath days, it seems that if I am going to be great in the kingdom, I should obey and teach them (Matthew 5:17-20); however it also seems that Jesus Himself taught that the sabbath is not all-important, and that neither are the food laws.
It seems to be kind of like the teaching Jesus gave about whether to be an eunuch or not. "He that is able to receive it, let him receive it."
Those who break the least of these commandments and teach men so will not be excluded from the kingdom (in Matthew 5:17-20); but they will be called least in the kingdom.
God is wanting to bring back His Jewish people into the fold of those accepted by Him through faith in the Messiah. In 1 Corinthians 8 and Romans 14, we are told to be sensitive to the consciences of our weaker brothers and sisters (those who feel that the food laws define what is clean and unclean; or those who hold the sabbath day above other days). Perhaps even to the extent of observing these laws ourselves, since at any moment we might come into contact with a weaker brother or sister, who may be stumbled by our liberty, their conscience being emboldened to eat what they do not in reality have liberty to eat. We ought to bear the infirmities of the weak and not to please ourselves, even if we ourselves are stronger and feel that we have the liberty to eat what is unclean or to work on Saturday. Jesus did say that it is lawful to do well, what is good and right, on the sabbath days. He redefined the sabbath for us; He is the Lord of the sabbath; I am not certain that He abolished it completely. It is an excellent principle to follow that we should set aside time to rest and spend time with the Lord between Him and us alone. And food laws are now reduced to being an indicating factor of whether or not we have the love of God in our hearts towards a weaker brother, since in 1 Timothy 4:1-6 it becomes clear that 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. So as Gentile believers we have the right to eat what our culture tells us is good; while if we know that we even might be in the presence of a weaker (Jewish) brother or sister we ought to be sensitive to their consciences and refrain from eating what we might otherwise have liberty to eat.
And Jesus healed on the sabbath, even though it stumbled the scribes and Pharisees who were looking onward. However He was redefining the sabbath as the One who made it; because the scribes and Pharisees had taken it too far and had made an idol out of keeping strict laws concerning it. Paul's exhortation in Romans 14 concerning the sabbath is let every man be fully convinced in his own mind as to whether he holds one day above another or whether he holds every day alike. And the weaker brother is not to judge the stronger brother; and the stronger brother is not to hold the weaker brother in contempt.
