Brother, both sides of the debate! Those who keep Sunday and those who keep the tradition of Judaism outside of Israel's time zone have not entered the gospel, or the good news, of the call to "enter" into the "rest" of God's Sabbath, as those "whose corpses lay in the wilderness" for 40 years because of an "oath" before reaching the Promised Land.
Therefore, since a promise remains of entering His rest, let us fear lest any of you seem to have come short of it. For indeed the gospel was preached to us as well as to them; but the word which they heard did not profit them, not being mixed with faith in those who heard it. For we who have believed do enter that rest, as He has said: “So I swore in My wrath, ‘They shall not enter My rest,’ ” although the works were finished from the foundation of the world. For He has spoken in a certain place of the seventh day in this way: “And God rested on the seventh day from all His works”; and again in this place: “They shall not enter My rest.” Since therefore it remains that some must enter it, and those to whom it was first preached did not enter because of disobedience, again He designates a certain day, saying in David, “Today,” after such a long time, as it has been said: “Today, if you will hear His voice, Do not harden your hearts.” For if Joshua had given them rest, then He would not afterward have spoken of another day. There remains therefore a rest for the people of God. For he who has entered His rest has himself also ceased from his works as God did from His. Let us therefore be diligent to enter that rest, lest anyone fall according to the same example of disobedience. (Hebrews 4:1-11 NKJV)
Those before Jesus "whose corpses lay in the wilderness" could not have entered what was still future. We must enter the "rest" in which they had not entered for 40 years by oath due to their disobedience. The only "rest" available to them as for us is the "rest" on the Sabbath.
And who made God angry for forty years? Wasn’t it the people who sinned, whose corpses lay in the wilderness? And to whom was God speaking when he took an oath that they would never enter his rest? Wasn’t it the people who disobeyed him? So we see that because of their unbelief they were not able to enter his rest. (Hebrews 3:17-19 NLT)
The "rest" they could have entered into as we "can" is the Sabbath "rest".
For only we who believe can enter his rest. As for the others, God said, “In my anger I took an oath: ‘They will never enter my place of rest,’” even though this rest has been ready since he made the world. We know it is ready because of the place in the Scriptures where it mentions the seventh day: “On the seventh day God rested from all his work.” (Hebrews 4:3-4 NLT)
United in our hope for the soon return of Jesus, Jorge