I’ve read Justin Martyr many times.
I also know that he was a dedicated anti-Semite, which would explain a lot of the early church’s attitude of hate toward all things Jewish, including the Sabbath.
Regardless, why quote someone who lived in the 2nd Century? What is wrong with the 1st Century account? Have you not read the book of Acts? Have you not read Paul’s own declaration in Acts 28, where he says that he had never abandoned the Law and traditions of the Jews?