"What justification do we have to move the Sabbath from Saturday to Sunday?"

This question is well addressed first with reference to that declaration of our Lord Jesus, "The Son of Man is Lord of the sabbath", Matthew 12:8, Mark 2:28, Luke 6:5.

Unlike the Pharisees to whom He originally said it, let us bring to this breathtaking statement a Gospel understanding of the identity of this "Son of Man": He is God incarnate. That understanding surely obviates any limiting of this sabbath lordship of which the Lord Christ spoke. For He is the One Who ordained the sabbath at the beginning, the One Who commanded that it be remembered at Sinai, the One Whose standard for the final judgment of all men will include the ordinance of the sabbath.

Thus it would seem likely that some change(s) pertaining to the fourth commandment might have occured along with the advent of God in the flesh, since, in the New Covenant Scriptures, He underscores His lordship of only this one of the ten commandments. In other words, the Son of Man is Lord (Lawgiver and Judge, Isaiah 33:22; cf. John 5:22,23; James 4:12) of commandments one through three, and five through ten also. However, He in Whom are hidden all the treasures of wisdom and knowledge (Colossians 2:3), Who indeed is the wisdom of His people (1 Corinthians 1:30), makes no "proactive" statement regarding those nine commandments.

"Christ is the end of the law for righteousness to everyone who believes", Romans 10:4. Those in Him are not under law, but grace. Yet Paul the apostle first wrote, "Do we then make void the law through faith? Certainly not! On the contrary, we establish the law", Romans 3:31. Christ's advent made no change to the essence of God's eternal moral standard for Man, which is summed up by the ten commandments. Adultery and stealing are still to be abhorred, even more so under the Gospel, by the constraining power of Christ's love. Faithfulness and watching out for my neighbor's property (cf. Exodus 23:4) are still to be practiced diligently -- with even more zeal and delight, on account of the same constraint.

(Thanks be to God Who will perfect His saints who bemoan their present shortcomings to such obedience. In His time, He will complete the work of conforming them to Jesus in holiness, to live and worship in the beauty of holiness and light, in His thrice holy heaven, that eternal sabbath rest that remains for the people of God!)

The point is this: a change regarding which day of the week the sabbath is observed presents to the mind that loves God's law no essential moral change. So it would seem that the New Testament, "without comment", simply upholds nine commandments unchanged, but presents a non-moral change regarding the one commandment.

To these observations let us add the precept that Scripture teaches not only by direct statement, but by "good and necessary consequence", i.e. valid inference. For instance, in John chapter 10, adversaries of the Lord Jesus cry, "For a good work we do not stone You, but for blasphemy, and because You, being a Man, make Yourself God." Surely if the Master was indeed a man only, and especially if He were a good man, He swiftly would have cried out to correct their "misunderstanding". That He does not do so speaks volumes to us by inference: namely that the Teacher is in fact God! He Who accepted the worship of Thomas with approbation, John 20:28, is the great I AM!

Moreover, Scripture teaches not only by direct statement and by inference, but by a third way, example:

1 Corinthians 10:6 & 11, minding the reader of the exodus experience of Israel - "Now these things became our examples, to the intent that we should not lust after evil things as they also lusted...Now all these things happened to them as examples, and they were written for our admonition, upon whom the ends of the ages have come."

Hebrews 6:12 "...that you do not become sluggish, but imitate those who through faith and patience inherit the promises."

1 Thessalonians 2:14 - "For you, brethren, became imitators of the churches of God which are in Judea in Christ Jesus..."

Hence, bearing in mind the apostolic commendation of the Thessalonians as imitators of the practice of the Judaean (earliest) congregations, let us consider these verses:

1 Corinthians 16:1,2 "Now concerning the collection for the saints, as I have given orders to the churches of Galatia, so you must do also: On the first day of the week let each one of you lay something aside, storing up as he may prosper, that there be no collections when I come."

Acts 20:7 Now on the first day of the week, when the disciples came together to break bread, Paul, ready to depart the next day, spoke to them and continued his message until midnight.

The apostolic orders given, and examples seen, teach us that it is normative for the churches to gather to "break bread" (participate in the eucharistic meal), to hear the word of God preached, and to give, all on the first day of the week.

It was on the first day of the week that the Lord of the Sabbath rose from the dead (Matthew 28:1-7; Mark 16:2, 9; Luke 24:1; John 20:1). And surely Immanuel's coming into the world, and the salvation He accomplished (gloriously heralded by His resurrection) are Divine works greater than the giving of the Law at Sinai...works even greater than creation itself and its accompanying primeval commandments to Man. True, no sentence appears in the New Testament, "change the sabbath to the first day of the week in view of My resurrection on that day", but consider the following also -

The fact that Jesus' resurrection appearance to His disciples was on the first day of the week is specifically mentioned (John 20:19).

He appeared again to the eleven disciples eight days after that. The Jewish way of counting days (i.e. the day on which you begin the count is not "zero", but one) means that it was again the first day of the week, "Sunday" (John 20:26).

The Holy Spirit came with power on Pentecost, on the first day of the week (Acts 2:1, cf. Leviticus 23:16). That same day saw what might be considered the first Christian sermon, by the apostle Peter, verse 14, and the baptisms of the those three thousand converts, verse 41.

It is almost in passing, it seems, that the apostle John mentions just when his extraordinary vision, the apocalypse (book of Revelation) occured:

Revelation 1:10 "I was in the Spirit on the Lord's Day, and I heard behind me a loud voice, as of a trumpet"

What is this "Lord's day" to which the apostle John refers? History is not our inspired authority, but history confirms the only reasonable conclusion, that this phrase is a reference to the first day of the week.

Hence it appears that the first day of the week is the Lord's day, the Christian sabbath, a Gospel ordinance which also remains for the people of God on Earth until He comes.