In 1 Corinthians 16:1–3, the apostle Paul writes,
“Now concerning the collection for the saints, as I have given orders to the churches of Galatia, so you must do also: 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. And when I come, whomever you approve by your letters I will send to bear your gift to Jerusalem.”
In this passage, the apostle was writing a special appeal to the churches in Asia Minor. Famine conditions were not unusual in areas of the Middle East (see Acts 11:28–30), and at the time, many of the Christians in Jerusalem were suffering greatly. Paul asked the church at Corinth to “lay something aside” until he could send helpers to transport the collection to Jerusalem. The expression "lay something aside" in the original Greek comes with the connotation of putting something aside at home. Even Sunday-worship advocates agree with this interpretation.
Thus, there was no religious meeting held on the first day of the week and no collection plate passed at church on Sunday. Instead, they were to gather and store up their donations at home on that day.
If there was no religious meeting on Sunday, why did Paul specifically suggest that this work be done on Sunday? Simply, the letter would have been shared with the church on the Sabbath when they were all gathered for worship, and the first opportunity for them to do the work would be the next day—the first day of the week.
“Now I am going to Jerusalem to minister to the saints. For it pleased those from Macedonia and Achaia to make a certain contribution for the poor among the saints who are in Jerusalem. It pleased them indeed, and they are their debtors. For if the Gentiles have been partakers of their spiritual things, their duty is also to minister to them in material things. Therefore, when I have performed this and have sealed to them this fruit, I shall go by way of you to Spain" (Romans 15:25–28).
Here the apostle touched a tender spot in his eloquent appeal. The Roman Christians owed a great debt of gratitude to the church in Jerusalem, which had sent teachers to evangelize them. Paul urged them to return material gifts in appreciation of the spiritual truths received. He described it as sealing to them "this fruit." The Greek word used here is "karpos," which is the universal term used for literal fruit. It can also have the connotation of "fruits of one's labor."
Thus, in these verses, the reference to the day of Sunday gives no indication of a change in religious observance.