Q: Which day of the seven hath God appointed to be the weekly sabbath?
A: From the beginning of the world to the resurrection of Christ, God appointed the seventh day of the week to be the weekly Sabbath; and the first day of the week ever since, to continue to the end of the world, which is the Christian Sabbath.

Genesis 2:2. And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made.
Luke 23:56. And they returned, and prepared spices and ointments; and rested the sabbath day according to the commandment.
Acts 20:7. And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
1 Corinthians 16:1-2. Now concerning the collection for the saints, as I have given order to the churches of Galatia, even so do ye. Upon the first day of the week let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come.
John 20:19-26. Then the same day at evening, being the first day of the week, when the doors were shut where the disciples were assembled for fear of the Jews, came Jesus and stood in the midst, and saith unto them, Peace be unto you. And when he had so said, he shewed unto them his hands and his side. Then were the disciples glad, when they saw the Lord. Then said Jesus to them again, Peace be unto you: as my Father hath sent me, even so send I you. And when he had said this, he breathed on them, and saith unto them, Receive ye the Holy Ghost: whose soever sins ye remit, they are remitted unto them; and whose soever sins ye retain, they are retained. But Thomas, one of the twelve, called Didymus, was not with them when Jesus came. The other disciples therefore said unto him, We have seen the Lord. But he said unto them, Except I shall see in his hands the print of the nails, and put my finger into the print of the nails, and thrust my hand into his side, I will not believe. And after eight days again his disciples were within, and Thomas with them: then came Jesus, the doors being shut, and stood in the midst, and said, Peace be unto you.

Westminster Project - See Matthew Henry's Scripture Catechism based on the WSC for more textual support for question 59