What does Isaiah 6:13 mean?
When Isaiah has asked the Lord, "How long?", he seems to have meant how long he must keep preaching about God's coming judgment. The Lord has said that Isaiah must continue preaching until judgment comes in the form of the people being carried off into exile and the land being left in desolation and emptiness (Isaiah 6:11–12).If even a ten percent of the people remain in the Lord, judgement will come again. In mentioning the terebinth tree and the oak, the Lord is describing a forest that has been cut down and the remaining stumps are burned to keep them from growing back. The destruction left behind offers little hope of new life.
However, these harsh verses of warning end with the slightest hope, "the holy seed is its stump". In other words, out of the burned remains of one of the trees of Judah, metaphorically speaking, a shoot of new growth will spring up.
Though the people of his generation will not respond to his preaching, the hope of Isaiah's messages rest in this "holy seed". This "seed" points to the coming Messiah who will bring salvation to the world.