"could not be separated, and that the time for the commandments of God to shine out with all their importance, and for God's people to be tried on the Sabbath truth, was when the door was opened in the most holy place in the heavenly sanctuary, where the ark is, in which are contained the ten commandments. This door was not opened until the mediation of Jesus was finished in the holy place of the sanctuary in 1844. Then Jesus rose up and shut the door of the holy place, and opened the door into the most holy, and passed within the second veil, where He now stands by the ark, and where the faith of Israel now reaches. EW 42.1"
"And over it the cherubims of glory shadowing the mercyseat; of which we cannot now speak particularly."
Both passages refer to the ark and the cherubim shadowing the mercy seat within the sanctuary. While Hebrews 9:5 is a description, EGW's passage builds upon this imagery to explain the significance of the heavenly sanctuary and its connection to the commandments. The connection is thematic, as EGW uses the imagery from Hebrews to support her theological claims.
"I saw that Jesus had shut the door of the holy place, and no man can open it; and that He had opened the door into the most holy, and no man can shut it ( Revelation 3:7, 8 ); [See page 86 . See also Appendix .] and that since Jesus has opened the door into the most holy place, which contains the ark, the commandments have been shining out to God's people, and they are being tested on the Sabbath question. EW 42.2"
"And to the angel of the church in Philadelphia write; These things saith he that is holy, he that is true, he that hath the key of David, he that openeth, and no man shutteth; and shutteth, and no man openeth;"
EGW explicitly quotes and references Revelation 3:7, applying it to Jesus' ministry in the heavenly sanctuary. This is a clear and direct allusion.
"I saw that the present test on the Sabbath could not come until the mediation of Jesus in the holy place was finished and He had passed within the second veil; therefore Christians who fell asleep before the door was opened into the most holy, when the midnight cry was finished, at the seventh month, 1844, and who had not kept the true Sabbath, now rest in hope; for they had not the light and the test on the Sabbath which we now have since that door was opened. I saw that Satan was tempting some of God's people on this point. Because so many good Christians have fallen asleep in the triumphs of faith and have not kept the true Sabbath, they were doubting about its being a test for us now. EW 42.3"
"There remaineth therefore a rest to the people of God."
Both passages discuss rest for God's people. Hebrews 4:9 speaks of a general rest, while EGW applies this concept to those who died before the Sabbath truth was fully revealed. The connection is thematic, as EGW uses the idea of rest to explain the situation of past believers.