"The forms of Moses and Eleazar were at last discerned, slowly descending the mountainside, but Aaron was not with them. Upon Eleazar were the sacerdotal garments, showing that he had succeeded his father in the sacred office. As the people with heavy hearts gathered about their leader, Moses told them that Aaron had died in his arms upon Mount Hor, and that they there buried him. The congregation broke forth in mourning and lamentation, for they all loved Aaron, though they had so often caused him sorrow. “They mourned for Aaron thirty days, even all the house of Israel.” PP 427.1"
"And when all the congregation saw that Aaron was dead, they mourned for Aaron thirty days, even all the house of Israel."
The EGW passage directly quotes Numbers 20:29 and provides context for the verse within the narrative of Aaron's death.
"the most illustrious men that ever lived, there were only two of his nearest friends to witness his death and to attend his burial. And that lonely grave upon Mount Hor was forever hidden from the sight of Israel. God is not honored in the great display so often made over the dead, and the extravagant expense incurred in returning their bodies to the dust. PP 427.2"
"And he buried him in a valley in the land of Moab, over against Beth–peor: but no man knoweth of his sepulchre unto this day."
The EGW passage draws a parallel between the hidden burial of Moses (Deuteronomy 34:6) and the idea that God is not honored by extravagant displays over the dead. While not a direct quote, the connection is clear and meaningful.
"Soon after leaving Mount Hor the Israelites suffered defeat in an engagement with Arad, one of the Canaanite kings. But as they earnestly sought help from God, divine aid was granted them, and their enemies were routed. This victory, instead of inspiring gratitude and leading the people to feel their dependence upon God, made them boastful and self-confident. Soon they fell into the old habit of murmuring. They were now dissatisfied because the armies of Israel had not been permitted to advance upon Canaan immediately after their rebellion at the report of the spies nearly forty years before. They pronounced their long sojourn in the wilderness an unnecessary delay, reasoning that they might have conquered their enemies as easily heretofore as now. PP 427.4"
"And when king Arad the Canaanite, which dwelt in the south, heard tell that Israel came by the way of the spies; then he fought against Israel, and took some of them prisoners."
Both passages describe a battle with King Arad after the death of Aaron and the Israelites' subsequent murmuring. EGW provides more context and interpretation, but the core narrative elements align.