Robin Parry’s major focus, in his book The Evangelical Universalist  , is a biblical case for universalism, and that means one eventually has to take a good hard look at the Old Testament.

45:20 Gather together and come!

Approach together, you refugees from the nations!

Those who carry wooden idols know nothing,

those who pray to a god that cannot deliver.

45:21 Tell me! Present the evidence!

Let them consult with one another!

Who predicted this in the past?

Who announced it beforehand?

Was it not I, the Lord?

I have no peer, there is no God but me,

a God who vindicates and delivers;

there is none but me.

45:22 Turn to me so you can be delivered,

all you who live in the earth’s remote regions!

For I am God, and I have no peer.

45:23 I solemnly make this oath –

what I say is true and reliable:

‘Surely every knee will bow to me,

every tongue will solemnly affirm;

45:24 they will say about me,

“Yes, the Lord is a powerful deliverer.”‘”

All who are angry at him will cower before him.

45:25 All the descendants of Israel will be vindicated by the Lord

and will boast in him.

Notice v. 23: this is an oath of YHWH, not just a hope that the nations will respond. All will bow and all will confess and all will say “the Lord is my righteousness and my strength” (alternative translation). He sees a kind of universalism at work here. [He has other texts too, but this is probably enough to see the direction. He also states that it was only with development in the belief of resurrection that a full universalism emerges.]