A generation ago the battle cry went up again when SDA scholar Samuele Bacchiocchi published a dissertation called From Sabbath to Sunday. It was a remarkable accomplishment considering Bacchiocchi carried out his studies at the Pontifical Gregorian University in Rome. Shortly thereafter screams of outrage emerged from the evangelical establishment, and Zondervan released a volume, edited by D. A. Carson, with the title From Sabbath to Lord's Day. More recently Henry Sturcke, a former Worldwide Church of God minister, stirred the embers with his own dissertation, published by Theologischer Verlag Zurich (TVZ) entitled Encountering the Rest of God.
As far as I recollect, none of these authors mentioned a possible Mandaean connection.
The Mandaeans are a little-known community that traces its origins back to John the Baptist. While that claim is sometimes disputed by Christian and Islamic scholars, there's no doubting that the Mandaeans themselves believe it, and that they have long been a feature on the religious landscape in Iraq (though now increasingly forced into diaspora.)
Here's a brief excerpt from the second chapter of the Mandaean Book of John. The words are ascribed to John the Baptist.
I stand by the authority of my father and with the commendation of my creator, The Man. I have built no house in Judea, nor founded a throne in Jerusalem. I have no love for the rosy wreath, nor the company of beautiful women. I have not loved imperfection, nor the cup of the drunkard. I have not loved the food of the body, nor has envy any foothold in me. I have not neglected my vespers, nor left the wondrous Jordan. I have not shirked my baptizing, nor the sealing with the sign of purity.So far, so gnostic. But then the text states.
I have not forgotten Sunday and its evening has not accused me of neglecting it. (Translation by Robert Price in The Pre-Nicene New Testament.)An editorial footnote reads; "Sunday is the holy day of the Mandaeans, who follow the Essene custom of bowing to the rising sun each day. Christians came from the same sectarian matrix and seem to have retained Sunday worship, later locating the resurrection of Jesus on that day to give it a uniquely Christian meaning."
It is, to say the least, an intriguing suggestion.