Please note, the word "Sunday" is not mentioned in the Bible at all, but there are eight New Testament texts that mention the "first day." Let us look at them briefly for evidence of Sun­day worship or holiness.
Browse: Who changed the Sabbath to Sunday?

First day Bible verses

1. Matthew 28:1
2. Mark 16:1-2
3. Mark 16:9
4. Luke 24:1
5. John 20:1
6. John 20:19
7. Acts 20:7, 11, 13
8. 1 Corinthians 16:1-2

1) 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” (Matthew 28:1).

There is no mention of Sunday sacredness in this text and no reference to worship in any form. Matthew 28:1 merely states that before sunrise on the first day these women came to examine the tomb.

2) Mark 16:1-2

“Now when the Sabbath was past, Mary Magdalene, Mary the mother of James, and Salome bought spices, that they might come and anoint Him. Very early in the morning, on the first day of the week, they came to the tomb when the sun had risen” (Mark 16:1-2).

These verses tell us that the first day of the week follows the Sabbath. They also inform us that these women had come on the morning of the first day pre­pared to embalm the body of Jesus, quite a task for those who should have rested if Sunday had any Bible sacred­ness. These women had no thought of Sunday sacredness.

3) Mark 16:9

“Now when He rose early on the first day of the week, He appeared first to Mary Magdalene, out of whom He had cast seven demons” (Mark 16:9).

Again, there is no mention of a day of rest here. Surely, if Jesus had intended that Sunday should be ob­served as a day of rest commemorating His resurrection, He would have told His disciples first of all. There is no Scriptural hint that they ever dreamed of a possible change of the Sabbath.

4) Luke 24:1

“Now on the first day of the week, very early in the morning, they, and certain other women with them, came to the tomb bringing the spices which they had prepared” (Luke 24:1).

Luke agrees with the other witnesses regarding the intention of these intimate friends and followers of Jesus. They had come to the tomb bent on giving the body of Jesus proper burial. In Luke 23:56, the verse just pre­ceding this text, we are told that these loyal disciples of Jesus "rested the Sabbath day according to the command­ment." Then, on the next day after the Sabbath, they were prepared to engage in a difficult day's work. This verse certainly offers no hint of the change of the Sabbath to the first day of the week.
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5) John 20:1

“Now the first day of the week Mary Magdalene went to the tomb early, while it was still dark, and saw that the stone had been taken away from the tomb” (John 20:1).

This text was evidently written about sixty years after the resurrection of Jesus. Yet John never so much as im­plied any knowledge of a Sabbath change. The disciple who felt himself closest to Jesus, evidently had never heard of a first-day commemoration of the resurrection.
Browse: Was the Sabbath nailed to the cross?

6) John 20:19

“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, Jesus came and stood in the midst, and said to them, ‘Peace be with you’” (John 20:19).

The doors were shut where the disciples were assem­bled for fear of the Jews. In Mark 16:14, we find Jesus reproving His disciples for their failure to believe that He had risen. There is, therefore, no possible chance that they had gathered on this occasion to commemorate the resurrection.

As we have seen from the previous verses, nowhere in the four Gospels is there the minutest hint of Sunday sacredness.

7) Acts 20:7, 11, 13

“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… Now when he had come up, had broken bread and eaten, and talked a long while, even till daybreak, he departed… Then we went ahead to the ship and sailed to Assos, there intending to take Paul on board; for so he had given orders, intending himself to go on foot” (Acts 20:7, 11, 13).
Read more: Did the disciples worship on Sunday in Acts 20:7-11?

8) 1 Corinthians 16:1-2

“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” (1 Corinthians 16:2).
Read more: Does Paul condone Sunday worship in 1 Corinthians 16:2?

Conclusions about New Testament Sunday worship

1. The disciples had no plans to make Sunday a day of worship.
2. There is no hint in the New Testament that the disciples or Jesus changed the day of worship from Sabbath to Sunday.
3. Nowhere in the New Testament is there a command to worship on Sunday as a memorial to the resurrection of Jesus.
4. Since there is no scriptural evidence that the disciples changed the worship of Sabbath to Sunday, this change must have been accepted in the Christian church after the Bible was written and all the disciples had died.