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 day. 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. According to this verse, 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 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 planning to give the body of Jesus a 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 written about sixty years after the resurrection of Jesus. Yet John, the disciple who considered himself closest to Jesus, never so much as implied any knowledge of a change to the Sabbath rest day.
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 reason for the assembly of the disciples in this instance is not to worship but out of 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 even a 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).
 

Many believe that the sacredness of the Sabbath, the seventh day of the week, was moved to Sunday, the first day of the week, by the disciples after Jesus’s death, resurrection and ascension to heaven. However, these verses from Acts say nothing about such a change. Many say that the breaking of bread and Paul’s preaching means that it was a sacred day. But Acts clearly states that the early believers broke bread every day (Acts 2:46) and Paul was preaching on this occasion because it happened to be his last visit with these Ephesian believers before he was eventually taken to Rome where he would die a martyr’s death. He preached for as long as he could until it was time for his painful goodbye to the believers. There is no mention that the purpose of this meeting was to celebrate a holy day.

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).
 

Many people have proposed that this verse speaks of worship on Sunday because it speaks of taking up an offering. But notice that Paul is telling the believers to save some money and store it up in their homes so that he doesn’t have to take up an offering when he comes. The money will be ready to give. He just chooses the first day of the week for them to actively set some money aside. Again, this verse does not mention any change of the Sabbath from Saturday to Sunday, nor does it say the believers should worship on Sunday.

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.