The Apostles themselves in acts changed the day they observed from sat to Sunday, and theuy had the authority to do that, but EW has NO authority to place us back under the bondage of the law!Your pointing out unity after the cross in scriptures, is interesting. That one major teaching(supposedly) made from Christ(after the resurrection) is NOT common among all the disciples(even the words after the cross from Jesus) in scripture canon.
But is in common with Christians today, Sunday rest and holiness. Which prophecy tells, that a coming death decree will be over that human behavior. Go ahead and deny it. My reward is when GOD's prophecy come true, and GOD decides a person's salvation over it.
AV Ro 13:8-10 Owe no man any thing, but to love one another: for he that loveth another hath fulfilled the law. 9 For this, Thou shalt not commit adultery, Thou shalt not kill, Thou shalt not steal, Thou shalt not bear false witness, Thou shalt not covet; and if [there be] any other commandment, it is briefly comprehended in this saying, namely, Thou shalt love thy neighbour as thyself. 10 Love worketh no ill to his neighbour: therefore love [is] the fulfilling of the law.
That is because, murder is a VALID commandment to Christians in their understanding of the lack of love towards "thy neighbour".
Conclusion: There is NO UNITY of Sunday rest among Jesus' words(neither before or after the cross) and among the words of all the disciples(after the cross) in the canon of scriptures.
Another prophecy is: What looks like Jesus(actually satan) realizing his mistake in Sunday rest in scriptures, will come among Christian and pronounce the change from sabbath to Sunday. Which will go against every prophecy of Jesus' actual second advent, in scriptures, go figure spiritually that one.
I will be here to help any through their cognitive dissonance in fulfilled prophecy. The irony is nominal Christians will make it come true !!!
Yours in Christ, Michael