Precedence
The verses Rom. 14:4-6 and Col. 2:16, 17 are the weapons (the sword of the spirit, which is the word of God) of a holy war--a perpetual, spiritual crusade against legalism, invading the stronghold of enmity of unprofitable traditions which have withstood grace and truth throughout Christiandom. The Christian ministry does not consist of hand-to-hand combat: our warfare is according to the fashion of the spiritual battle mentioned in II Cor. 10:3-6, for instance, "we demolish sophistries and all that rears its proud head against the knowledge of God" (II Cor. 10:5 [NEB]). See Eph. 6:10-18.
Both the sabbath and the first day of the week have an underlying significance, which is the person whom each points toward: the former in anticipation of Christ; and the latter in retrospect to Him. However, the first day of the week was the day appointed by Paul for collection, according to the prosperity the Lord had given Christians at Corinth: "Upon the first day of the week let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come" (1 Cor.16:2 [KJV]).
I have had several contemplations concerning the term the "Lord's day," mentioned only once in the New Testament: "I was in the Spirit on the Lord's day ... " (Rev. 1:10 {KJV]). I have re-written my former thoughts concerning this verse in case I may have seemed to have been presumptuous previoulsy. Perhaps it denotes a day other than the sabbath, such as connoting the commemoration of the day of the Lord's resurrection or some other memorial, but I do not know. Another comtemplation is that perhaps it is a day that belongs explicitly to God, rather than to Jesus.
However, it is easily understood that the author of the book of Hebrews attributed (having known the old covenant law) the sabbath day as the seventh day of the week: see Ex. 20:11. Jesus said, "It is finished" his last moment on the cross. He completed his work that God had given him to do in order that we might have life. God completed all the creation in six days and he rested on the seventh day. Jesus is the "rest" people need to enter!
"It is we, we who have become believers, who enter the rest referred to in the words, 'As I vowed in my anger, they shall never enter my rest.' Yet God's work has been finished ever since the world was created; for does not Scripture somewhere speak thus of the seventh day: 'God rested from all his work on the seventh day'?" (Heb. 4:3, 4 [NEB])
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