A minority still advocate that worshiping on Sunday is in violation of God's law to keep the Sabbath (the seventh day of the week) holy. However, I believe that ceased at the moment Christ died on the cross. Perhaps you remember in Matthew what happened the instance Christ gave up the ghost:  

   ⁵⁰Jesus, when He had cried out again with a loud voice, yielded up the ghost.    ⁵¹And behold, the veil of the temple was rent(or torn)in two from the top to the bottom, and the earth quaked and the rocks rent.   ⁵²And the graves were opened; and many bodies of the saints who slept arose,      ⁵³and came out of the graves after His resurrection, and went into the Holy city  and appeared unto many.     ⁵⁴Now when the centurion, and those who were with him watching Jesus, saw the earthquake and those things that were done, they feared
The two significant verses so far as Sunday worship is concerned are "51"
and "52".  Notice that the "veil of the temple was rent or torn in two from top to the bottom.  We know from  John's description of Heaven in Revelationas well as several Old Testament passages that the temple was laid out to be symbolic of Heaven.  The veil of the
temple separated the room known as the "holy of holies" from the rest of the temple.
It was the room where God dwelt and it was accessible to anyone but the>high priest ,who could only enter it once a year to offer sacrifices to atone for the previous years'  sins of the Israelites.
When >Christ gave up the ghost on the cross, however, his sacrifice became >our atonement, providing instant access for all to God. The temple's significance no longer existed to block man from direct access to God.
In Verse 52 we learn that the graves were opened and many bodies of the saints who slept there arose.  These were the faithful of the Old Testament who are now in Heaven in both body and soul with God.  Notice that the bodies of the wicked did not arise. They are condemned forever to death. Their souls, however, are now in Hades, where they suffer while awaiting the end of the world, at which time they will be judged and cast into the "lake of fire." or hell.The Old Testament Dispensation ended with Christ's death and so did the
We know, however, that the Apostles continued to keep the Sabbath as holy
as well as follow the old laws, most notably those regarding what food
was clean.   Even Paul, who understood the Old Law better than anyone
and realized that it was no longer applicable, would go into the
temples on Saturday to preach to the people.  However,  that seems
logical because he first was reaching out to the Jews and that was
where he would find them.
After
the Jews rejected Paul, trying to capture and kill him for preaching
heresy, he fled back to Asia Minor, his home.  There, after his first >missionary trip where he again was persecuted by ews, he abandoned br>them and took his message to the Gentiles.

As more and more Gentiles converted to Christianity, they began to meet in homes and the references to what day they met are more obscure.
Soon,a serious difference of opinion developed between the Jerusalem church regarding the keeping of the Jewish Law.  The Jerusalem church, headed by James, the brother of Jesus, basically continued to follow the Jewish Law while patiently waiting for Christ's return, which they thought was imminent and would happen in their lifetime. They were not thrilled at the prospect of Paul taking the good news to the Gentiles, whom the Jews had always considered unclean because they ate forbidden food and did not circumcise their children.
Had >not Peter, who had been instructed in a dream regarding what food could now be eaten and had also been instructed in the dream to go to the Roman centurion Cornelius' home, who was a Gentile believer, to dine with him, to spend time there and to baptize his household, Paul's work with the Gentiles might have ceased./span> .
Though it would be almost a hundred years before Christians began to believe that the keeping of the Sabbath might not be necessary, the seeds for Sunday worship were now in place.
(To Be Continued)