I have been wanting to get back with you about this issue and share a few observations. I have not been avoiding it, but rather been waiting to see if what I want to say will be my thoughts still after a few days. AND I also have been so very busy with harvesting tomatoes and pecans - the trees have produced abundantly this year.
Now to the issue of 'Sabbath keeping' whether it be on Saturday or Sunday....
It has been my observation that when people who are relatively new to the faith, be they from apostate churches or from American intellectualism, there is a strong resistance to the observance of any NT 'ritual' because it simply does not make sense. AND this is nothing new.
Consider Bro. Peter. In John 13 Jesus with his disciples observed the passover and after doing so, "Jesus got up from supper, and laid aside His garments; and taking a towel, He girded Himself. Then He poured water into the basin, and began to wash the disciples' feet and to wipe them with the towel with which He was girded. And so he came to Simon Peter. He said to him, "Lord, do you wash my feet?" Jesus answered and said to him, " What I do you do not realize now, but you shall understand hereafter." Peter said to Him, "Never shall You wash my feet!" Jesus answered him, "If I do not wash you, you have no part with Me." Simon Peter said to Him, "Lord, then wash not only my feet, but also my hands and my head." Jesus said to him, "He who has bathed needs only to wash his feet, but is completely clean; and you are clean, but not all of you." (NASB)
What I want you to see here in this passage is Peters' resistance to Jesus washing his feet and his objections: OK, so you want to wash my feet; wash my head and my hands as well!" (My paraphrase.) You see these guys [likely] had clean feet - as I understand the custom a guest's feet were washed soon after being admitted into the house. The timing of this occasion was after supper. So they must have had clean feet and Peter knew it. It made no sense to wash clean feet. Now what is Jesus teaching him? Rather then going there in this discussion, my point is that sometimes the LORD will ask us to do "things in remembrance of Him!" And so it is with keeping a day Holy unto Him. This is what it is all about.
Hope this makes sense. And if it doesn't, make this a matter of prayer. I suggest you talk to the LORD about it and listen to what he may tell you to do. Just because some things make no sense does not mean it isn't sensible, it just means we are still a tad bit ignorant or that some things will never be understood on this side of glory, hence our need to be obedient in spite of it. And this act is called "faith".
This is my understanding of this concept.