I don't know. Maybe every generation until the veil is taken away in Christ Jesus.
I've been meaning to share my understanding of unbelieving Israel's blindness in part (in other words, until the fullness of the Gentiles be come in).
Paul is talking about their
willful disobedience to the call of the gospel.
The Lord said the same thing about them, at the end of John 5; as did the Spirit, through Stephen, near the end of Acts 7.
In other words, those of Israel who when reading the Law and the Prophets, refuse to believe that Jesus had been that Prophet their Law and the Prophets did say should come.
That is what Isaiah was talking about, Isaiah 8:19, 20.
Romans 10:19 But I say, Did not Israel know? First Moses saith, I will provoke you to jealousy by them that are no people, and by a foolish nation I will anger you. 10:20 But Esaias is very bold, and saith, I was found of them that sought me not; I was made manifest unto them that asked not after me. 10:21 But to Israel he saith, All day long I have stretched forth my hands unto a disobedient and gainsaying people.
Note this same dynamic in Acts 17.
Acts 17:1 Now when they had passed through Amphipolis and Apollonia, they came to Thessalonica, where was a synagogue of the Jews: 17:2 And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures, 17:3 Opening and alleging, that Christ must needs have suffered, and risen again from the dead; and that this Jesus, whom I preach unto you, is Christ. 17:4 And some of them believed, and consorted with Paul and Silas; and of the devout Greeks a great multitude, and of the chief women not a few. 17:5 But the Jews which believed not, moved with envy, took unto them certain lewd fellows of the baser sort, and gathered a company, and set all the city on an uproar, and assaulted the house of Jason, and sought to bring them out to the people.
This is what the spirit (heart attitude) of slumber refers to.
Just like the Gentiles in Romans 1: when they turned from God, He gave them over to their desired mind against Him - a reprobate mind: a mind not willing to be reproved in what it needs to hear.
And this is where things are for Israel and the world once more, after the Rapture, some point after which this takes place...
2 Thessalonians 2:8 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: 2:9 Even him, whose coming is after the working of Satan with all power and signs and lying wonders, 2:10 And with all deceivableness of unrighteousness in them that perish;
because they received not the love of the truth, that they might be saved. 2:11 And for this cause God shall send them strong delusion, that they should believe a lie: 2:12 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
In contrast to that willfulness are these people...
2:13 But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and
belief of the truth: 2:14 Whereunto he called you by our gospel, to the obtaining of the glory of our Lord Jesus Christ.
In contrast to those chosen to believe a lie for their having wanted to to begin with, are those chosen to salvation through the gospel for their having wanted to hear it.
Willful unbelief...
Acts 13:41 Behold, ye despisers, and wonder, and perish: for I work a work in your days, a work which ye shall in no wise believe, though a man declare it unto you.
Versus wanting to hear it...
13:42 And when the Jews were gone out of the synagogue, the Gentiles besought that these words might be preached to them the next sabbath.
Willful unbelief...
13:45 But when the Jews saw the multitudes, they were filled with envy, and spake against those things which were spoken by Paul, contradicting and blaspheming.
God's having turned from them for their continued uncircumcision of heart...
13:46 Then Paul and Barnabas waxed bold, and said, It was necessary that the word of God should first have been spoken to you: but seeing ye put it from you, and judge yourselves unworthy of everlasting life, lo, we turn to the Gentiles.
Paul's applying the following to himself...
13:47 For so hath the Lord commanded us, saying, I have set thee to be a light of the Gentiles, that thou shouldest be for salvation unto the ends of the earth.
Towards those wanting to hear it...
13:48 And when the Gentiles heard this, they were glad, and glorified the word of the Lord: and as many as were ordained to eternal life believed.
The principle being...
Romans 1:16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
God has ordained that those who believe the gospel of Christ will be saved by it.
He has built the power to save into the gospel of Christ - the power to save...them that believe, that is.
Romans 3:22 Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference: 3:23 For all have sinned, and come short of the glory of God; 3:24 Being justified freely by his grace through the redemption that is in Christ Jesus:
The gospel of Christ is the power of God...unto salvation - to everyone that believeth!
Amen! And Amen!
Wonder working power indeed!
Rom. 14:5; Rom. 5:6-8.