Justin was given as a historical fact that Christian’s from the first century worshipped on Domenica, not Sabbath.
>Matthew 28:1: “Now after the Sabbath, as the first day of the week began to dawn, Mary Magdalene and the other Mary came to see the tomb.”
Mark 16:2: “Very early in the morning, on the first day of the week, they came to the tomb when the sun had risen.”
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.”
I Corinthians 16:2: “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.”
Remember Mark 2:27 says, “The Sabbath was made for man, and not man for the Sabbath.” and
“One man regards one day above another, another regards every day alike. Let each man be fully convinced in his own mind. 6 He who observes the day, observes it for the Lord, and he who eats, does so for the Lord, for he gives thanks to God; and he who eats not, for the Lord he does not eat, and gives thanks to God,” (Rom. 14:5-6).
and
“Therefore let no one act as your judge in regard to food or drink or in respect to a festival or a new moon or a Sabbath day 17things which are a mere shadow of what is to come; but the substance belongs to Christ.” (Col. 2:16-17).
Jesus said that He was the Lord of the Sabbath and that He fulfilled the Law.
The disciples kept Domenica holy as is very clear in
Let no one, then, pass judgment on you in matters of food and drink or with regard to a festival or new moon or Sabbath (Col. 2:16)
The New Testament fulfilled the Law. Love God and your neighbour is reflected in the other commandments.