How does this idea of the key of David (Isaiah 22:20–22) translate to the local assembly at Philadelphia (Revelation 3:7)?

This text is from a transcript of a talk by David Gooding, entitled ‘The Salvation of the Lord’ (2001).

The letters to the churches in Revelation 2–3 are exceedingly interesting for their references to the Old Testament, are they not? And if you plot the references to the Old Testament throughout the seven letters, you will find that they come in order chronologically from Genesis to the exile of Israel to Babylon. In the letter to Ephesus, we read, 'To the one who conquers I will grant to eat of the tree of life, which is in the paradise of God' (Revelation 2:7). The word for 'paradise' is the word that the Greek translation uses for the garden of Eden.

The tree of life was in the garden of Eden, wasn't it? And when Adam and Eve sinned, they got shut out from the garden and from the tree of life. They got removed out of their place. In the first letter to Ephesus, therefore, the Old Testament allusion is to the tree of life in the garden of Eden, from which Adam and Eve got shut out. The warning to the church is, 'I will come to you and remove your lampstand from its place, unless you repent' (Revelation 2:5). And the promise to the overcomer is, 'I will grant to eat of the tree of life, which is in the paradise of God.'

Similarly, the oppression and the prison mentioned in the next church (Revelation 2:8–11) has, as its Old Testament counterpart, the word of God through the flaming torch and furnace at the covenant with Abraham (Genesis 15). He is told that his seed would be oppressed and have tribulation in a foreign land for a specific time, and then would come out. The Jews often take that as a specific reference to the furnace of the Egyptian affliction of the nation.

Church number three mentions Balaam and the way he taught Balak to cast a stumbling block before the Israelites (Revelation 2:14). And that, therefore, is a reference to the book of Numbers, chapter 22.

Church number four has a reference to Jezebel (Revelation 2:20). You have moved on to the book of Kings, haven't you?

Church number five is Sardis, whose works are not complete. The promise is, 'I will never blot his name out of the book of life' (Revelation 3:5). You'll find those terms used of the period in Israel around about Jeroboam the second. The works of the king before him were not complete. When he went to visit the dying Elisha, Elisha said, 'Take your arrows and smite them upon the ground.' And the good man took them and smote them three times, and then stopped. And Elisha rebuked him. 'You should have hit them on the ground six times, and then your enemy would have been consumed; but you gave up half way, didn't you? Your work is not complete.' And the history says in that time God began to cut Israel short, but he didn't eliminate them, for he said that he would not blot out their names (see 2 Kings 13:14–23).

Oh, but now you come to the key of the house of David. And this is later on now. It is 2 Kings. You have got beyond Jezebel and beyond Jeroboam the second, in Israel. But with the sixth church, that is Philadelphia, you have come to Hezekiah's time and 'the key of the house of David'.

And the last church is threatened with the Lord saying that if they did not repent, 'I will spit you out of my mouth' (Revelation 3:16), reminding us of what God said to the Israelites when they entered the land. In both Leviticus and again in Deuteronomy, he says, 'Don't you behave like the Canaanites, because if you do the land will spew you out like it did at the exile' (see Leviticus 18:28; Deuteronomy 28:36–37).

So, the references in the churches in Revelation 2–3 are going right through the Old Testament. They go along a chronological route, from Genesis to the exile. When we come to the notion of the house of David in the church of Philadelphia, my point is to say that the very allusion takes us back to the house of David and what it stood for among the nations. That is only a simple exposition and application, but when our Lord identifies himself in this way, that he has the key of David, he is pointing to what David stood for.