"When you had such evidences that God was waiting to be gracious to His people, that mercy's voice was inviting sinners and backsliders to the cross of Christ, why did you not unite with those who had the burden of the work upon them? Why did you not come up to the help of the Lord? Some of you seemed benumbed, stupefied, and amazed, and were unprepared to participate fully in the work. Many assented to it, but their hearts were not in it. This was a great evidence of the lukewarm condition of the church. 2T 216.2"
"So then because thou art lukewarm, and neither cold nor hot, I will spue thee out of my mouth."
Both passages discuss the negative consequences of being lukewarm in faith. EGW's passage directly addresses the lukewarm condition of the church, echoing the sentiment in Revelation 3:16.
"Your worldliness does not incline you to throw wide open the door of your hard hearts at the knock of Jesus, who is seeking an entrance there. The Lord of glory, who has redeemed you by His own blood, waited at your doors for admittance; but you did not throw them open wide and welcome Him in. Some opened the door slightly and permitted a little light from His presence to enter, but did not welcome the heavenly Visitor. There was not room for Jesus. The place which should have been reserved for Him was occupied with other things. Jesus entreated you: “If any man hear My voice, and open the door, I will come in to him, and will sup with him, and he with Me.” There was a work for you to do to open the door. For a time you felt inclined to hear and open the door; but even this inclination departed, and you failed to secure the communion with the heavenly Guest which it was your privilege to have. Some, however, opened the door and heartily welcomed their Saviour. 2T 216.3"
"Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me."
EGW directly quotes Revelation 3:20 and elaborates on the imagery of Jesus knocking at the door of the heart.