Is it a sin to take a bath on the Sabbath?

The statement you referred to is this one, from Testimonies for the Church, volume 6, pages 355, 356:

On Friday let the preparation for the Sabbath be completed. See that all the clothing is in readiness and that all the cooking is done. Let the boots be blacked and the baths be taken. It is possible to do this. If you make it a rule you can do it. The Sabbath is not to be given to the repairing of garments, to the cooking of food, to pleasure seeking, or to any other worldly employment. Before the setting of the sun let all secular work be laid aside and all secular papers be put out of sight. Parents, explain your work and its purpose to your children, and let them share in your preparation to keep the Sabbath according to the commandment.

When Mrs. White wrote this, many people here in America didn’t have convenient means for bathing. Consequently, they didn’t do it very often; perhaps once a week, some more often, and some less. For many people, taking a bath meant first heating the water on the stove or drawing it from a hot-water reservoir in their cookstove, transporting it to a large tub (in some cases one that was brought out into a room for this purpose), taking the bath, and then disposing of the water and cleaning up the area. There was considerable work involved in it. Some Adventist people delayed doing this on Friday, filling their day with regular work and leaving the bath for Friday night—after Sabbath had begun. Thus, they had two problems: first, they had a laborious chore to perform on the Sabbath, and second, they were not truly prepared in body and mind to welcome the Sabbath as sacred time when it came.

In many parts of the Western world today, these conditions do not exist. Water is heated automatically and flows into a bathtub at the turn of a valve. It also drains out of the tub with no ongoing effort by the person. These conditions have made bathing or showering a part of the daily routine of many people. In that respect, I personally feel that a morning shower is similar to washing one’s face in the morning or brushing one’s teeth. There is no labor involved in it, and it does not represent a lack of preparation for the Sabbath. Not everyone sees this question in the same light that I do. I have friends who are blessed in their practice of bathing before the arrival of the Sabbath and then not doing so on the Sabbath hours. I respect and honor their choice in this matter.

In the parts of the world where taking a bath still requires some laborious effort, I believe that it should be done before the arrival of the Sabbath, along with the other preparations that Mrs. White mentioned in the selection you read.

I have shared with you my own understanding of the matter. This is not an official position of the Ellen G. White Estate. I am not aware of the trustees of the White Estate having taken any official position on this point. You are welcome to consider the viewpoint I have expressed, but you are certainly also free to come to a different conclusion than mine regarding how we should apply Mrs. White’s statement to our situation today.