"Cleanliness The necessity of personal cleanliness was taught in the most impressive manner. Before gathering at Mount Sinai to listen to the proclamation of the law by the voice of God, the people were required to wash both their persons and their clothing. This direction was enforced on pain of death. No impurity was to be tolerated in the presence of God. MH 279"
"And the Lord said unto Moses, Go unto the people, and sanctify them to day and to morrow, and let them wash their clothes,"
EGW directly references the event and command in Exodus 19:10 regarding washing clothes before receiving the law at Mount Sinai.
"Thus shall ye separate the children of Israel from their uncleanness; that they die not in their uncleanness, when they defile my tabernacle that is among them."
Both passages emphasize the importance of separating from uncleanness to avoid death and defiling God's presence. While not a direct quote, the theme aligns.
"During the sojourn in the wilderness the Israelites were almost continually in the open air, where impurities would have a less harmful effect than upon the dwellers in close houses. But the strictest regard to cleanliness was required both within and without their tents. No refuse was allowed to remain within or about the encampment. The Lord said: MH 279.2"
"Thou shalt have a place also without the camp, whither thou shalt go forth abroad: And thou shalt have a paddle upon thy weapon; and it shall be, when thou wilt ease thyself abroad, thou shalt dig therewith, and shalt turn back and cover that which cometh from thee: For the Lord thy God walketh in the midst of thy camp, to deliver thee, and to give up thine enemies before thee; therefore shall thy camp be holy: that he see no unclean thing in thee, and turn away from thee."
EGW's statement about cleanliness within and around the Israelite camp directly reflects the instructions in Deuteronomy 23:12-14 regarding waste disposal outside the camp to maintain holiness.