The Sabbath or Lord's day is the day for man to rest in, and that, in the cessation from his ordinary labors, he may receive and be nourished by the truth, it is the day also for God to work in, in order that the truth may be communicated. God has a great message for his rebellious people; the message of life through his Son. But on the other days of the week, when their hands and their hearts are occupied with other things, it is difficult to obtain a hearing. It is on the Sabbath day, especially and emphatically, that this great message is communicated; — a message which involves in its results, not only the salvation of the soul, but equal rights among men, the emancipation of the enslaved, the, cessation of war, the progress of humanity and civilization, and universal brotherhood. All other forms of legitimate emancipation are necessarily involved in the emancipation of the soul from guilt and sin. Destroy the Lord's day, and you necessarily close the communications of God, which have relation to these great objects. You close the communications, because you take away the necessary opportunities for hearing them. He, therefore, who does anything on the Sabbath, which tends to interrupt the communication between God and men, by perplexing the operations of him who speaks or by diverting the attention of those who listen, does that which is inappropriate to the day.
The Sabbath is, in some respects, the great, the cheering hope of the human race. It is emphatically the day of the poor, the suffering, the enslaved, the prisoner. Without it, the poor man would scarcely have hope; laboring, as he would then be obliged to do, without cessation, and yet without additional emolument; — the slave, who experiences rest, and receives instruction on this day, would find his state of bondage more trying and distressing than ever; — the ignorant man, who greatly needs knowledge, would find many important avenues of knowledge closed to him; and the evils and sufferings which afflict our race would be, in various ways, greatly increased.
We may, perhaps, admit that the Sabbath, considered in its relations to the human race, was made for the unholy rather than for the holy. That is to say, the holy man, who has a perpetual Sabbath in his soul, could, perhaps, do without it, while the unholy man could not. But then it is to be remembered, that no man can properly be regarded as a truly religious or holy person, who has not a disposition to cooperate with God. Our great business is, to stand in union with him, who here and everywhere unfolds our destiny. If, therefore, it is the design of God to benefit men, especially the degraded and the sinful, through the medium of the Sabbath, it is justly expected of all who regard God's will and are like him, that they will observe and honor the Sabbath day. They cannot be united with him in spirit, without being united with him in the observance of this important institution; sympathizing in its objects, fulfilling its duties, and rejoicing in the hopes it inspires.
Edited from A Treatise on Divine Union (1851) Part 7, Chapter 5 by Thomas Cogswell Upham. His blog is managed by Craig L Adams and can be found here: http://thomascupham.blogspot.com