@Episkopos ..
I do not know whether your OP and thread title is meant to address Ephraim, part of the House of Joseph, part of the Kingdom (House) of Israel, as all future Non-Israelite believers (Gen 48:19 – “…his seed will become a multitude of nation”) or that Jesus is stumbling stone to non-believers of any tribe, of any blood, then or now – or both.
It is very confusing to weed out the Ephraim tribe within the Northern Kingdom of Israel, and then to say they will become, even all the future Non-Israelite believers, and then apply this entire premise to Isaiah Chapter 8. This is false and misleading.
You are cramming two major concepts into one discussion. They should be introduced separately, discussed separately, and then brought together later if desired.
I would keep Isaiah Chapter 8 in context with its historical perspective when discussing it. And it does apply today.
After Solomon died the 12 tribes were divided up into two distinct areas of land. The southern Kingdom of Judah comprised of Judah, Benjamin (and Levi). The Northern Kingdom of Israel compromised the other 10 tribes including Ephraim under the House/tribe of Joseph.
Now Isaiah 8 speaks to the 2 Houses or Kingdoms of Israel and Judah, and not specifically to the tribe of Ephraim within the House of Israel.
Those were the times of the Assyrian invasions where the Northern house/Kingdom -Israel already lost their trust in their God completely and relied on man-made political ties with Syria against Assyria. They were wanting the house/Kingdom of Judah to follow suit.
Isaiah Chapter 8 can be applied to all believers and non-believers in God. The concept of having faith, trust and time for and in God and not in self, man-made alliances do apply to all men/women, then and today.
Yes, Christ is either a stumbling stone to any non-believer whether those under the law or under grace today.
Verse 14 is all about a believer having faith in God for salvation and security, the altar becomes the sanctuary. The unbeliever in times of trouble relies on self and other men, and the altar is literally a pile of worn-out, unsafe stones to fall over, as a major hindrance, that can crush them. Ironically their self-reliance over their reliance in God forced their demise, their spiritual and physical capture and deaths.
(Isa 8:13) Yahweh of Armies is who you must respect as holy. He is the one you must fear; He is the one you must dread.
(Isa 8:14) He will be a sanctuary for both houses of Israel, but He will be a trap and a snare for the inhabitants of Jerusalem.
(Isa 8:15) Many will stumble over it, fall, be broken, be snared, and be captured. (NEV)
Since Christ, believers rely on Christ as their rock of salvation. To unbelievers, Christ is an obstacle to stumble over and slow them down, as a reminder of weakness, to avoid.
Now is not today the epitome of self-reliance, separation from God, the modern world defiant attitude of progress and success? Most are all racing to their doom; their capture, harm and deaths as did Israel of old.
As Peter wrote:
(1Pe 2:6) Because it is contained in scripture: Look, I lay in Zion a chief corner stone, chosen, precious. And he that believes in him shall not stumble.
(1Pe 2:7) Therefore, for you that believe he is precious. But to those who are disobedient, the stone which the builders rejected has become the chief cornerstone,
(1Pe 2:8) a stone of stumbling and a rock of offence. For being disobedient, they stumble at the word; to which they also were appointed.
(1Pe 2:9) But you are an elect race, a royal priesthood, a holy nation, a people for God's own possession, that you may show forth the excellence of Him who called you out of darkness into his marvellous light.
(1Pe 2:10) Who in times past were no people but now are the people of God. Who had not obtained mercy but now have obtained mercy. (ALL NEV)
Bless you,
APAK