Why today?

John 5:10–17 ESV

10 So the Jews said to the man who had been healed, “It is the Sabbath, and it is not lawful for you to take up your bed.” 11 But he answered them, “The man who healed me, that man said to me, ‘Take up your bed, and walk.’ ” 12 They asked him, “Who is the man who said to you, ‘Take up your bed and walk’?” 13 Now the man who had been healed did not know who it was, for Jesus had withdrawn, as there was a crowd in the place. 14 Afterward Jesus found him in the temple and said to him, “See, you are well! Sin no more, that nothing worse may happen to you.” 15 The man went away and told the Jews that it was Jesus who had healed him. 16 And this was why the Jews were persecuting Jesus, because he was doing these things on the Sabbath. 17 But Jesus answered them, “My Father is working until now, and I am working.”

Why do we gather on Sundays?

Acts 20:7–12 ESV

7 On the first day of the week, when we were gathered together to break bread, Paul talked with them, intending to depart on the next day, and he prolonged his speech until midnight. 8 There were many lamps in the upper room where we were gathered. 9 And a young man named Eutychus, sitting at the window, sank into a deep sleep as Paul talked still longer. And being overcome by sleep, he fell down from the third story and was taken up dead. 10 But Paul went down and bent over him, and taking him in his arms, said, “Do not be alarmed, for his life is in him.” 11 And when Paul had gone up and had broken bread and eaten, he conversed with them a long while, until daybreak, and so departed. 12 And they took the youth away alive, and were not a little comforted.

1 Corinthians 16:1–2 ESV

1 Now concerning the collection for the saints: as I directed the churches of Galatia, so you also are to do. 2 On the first day of every week, each of you is to put something aside and store it up, as he may prosper, so that there will be no collecting when I come.

Revelation 1:10 ESV

10 I was in the Spirit on the Lord’s day, and I heard behind me a loud voice like a trumpet

Lightfoot’s Apostolic Fathers in English 14

14. And on the Lord’s own day gather yourselves together and break bread and give thanks, first confessing your transgressions, that your sacrifice may be pure. 2And let no man, having his dispute with his fellow, join your assembly until they have been reconciled, that your sacrifice may not be defiled; 3for this sacrifice it is that was spoken of by the Lord; In every place and at every time offer Me a pure sacrifice; for I am a great king, saith the Lord, and My name is wonderful among the nations.

Holman Illustrated Bible Dictionary Lord’s Day

First, Ignatius in his Epistle to the Magnesians (about A.D. 110–117) stressed the importance of Lord’s Day by contrasting the worship done on that day with that formerly observed on the Sabbath

If then those who had walked in ancient practices attained unto newness of hope, no longer observing sabbaths but fashioning their lives after the Lord’s day, on which our life also arose through Him and through His death which some men deny—a mystery whereby we attained unto belief,

and for this cause we endure patiently, that we may be found disciples of Jesus Christ our only teacher if this be so, how shall we be able to live apart from Him? seeing that even the prophets, being His disciples, were expecting Him as their teacher through the Spirit. And for this cause He whom they rightly awaited, when He came, raised them from the dead. ~Lightfoot’s Apostolic Fathers in English

Ante-Nicene Fathers 1: The Apostolic Fathers with Justin Martyr and Irenaeus Chapter LXVII

And we afterwards continually remind each other of these things. And the wealthy among us help the needy; and we always keep together; and for all things wherewith we are supplied, we bless the Maker of all through His Son Jesus Christ, and through the Holy Ghost. And on the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read, as long as time permits; then, when the reader has ceased, the president verbally instructs, and exhorts to the imitation of these good things. Then we all rise together and pray, and, as we before said, when our prayer is ended, bread and wine and water are brought, and the president in like manner offers prayers and thanksgivings, according to his ability,2 and the people assent, saying Amen; and there is a distribution to each, and a participation of that over which thanks have been given, and to those who are absent a portion is sent by the deacons. And they who are well to do, and willing, give what each thinks fit; and what is collected is deposited with the president, who succours the orphans and widows, and those who, through sickness or any other cause, are in want, and those who are in bonds, and the strangers sojourning among us, and in a word takes care of all who are in need. But Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Saviour on the same day rose from the dead. For He was crucified on the day before that of Saturn (Saturday); and on the day after that of Saturn, which is the day of the Sun, having appeared to His apostles and disciples, He taught them these things, which we have submitted to you also for your consideration.

Galatians 5:13–14 ESV

13 For you were called to freedom, brothers. Only do not use your freedom as an opportunity for the flesh, but through love serve one another. 14 For the whole law is fulfilled in one word: “You shall love your neighbor as yourself.”

John 5:17 ESV

17 But Jesus answered them, “My Father is working until now, and I am working.”

Jesus isn’t just a man, He is God. He and the Father work everyday holding the universe together.