“For this thing the Lord himself shall give a sign to you. Lo! a virgin shall conceive, and shall bear a son; and his name shall be called Immanuel. [Lo! a maid(en) shall conceive, and bare a son; and thou shalt call his name Immanuel.]”
What is ‘this thing’ Isaiah mentions? ‘This thing’ is whatever wearies, not only men, but God.
“And Isaiah said, And so, hear ye, the house of David; is it not enough for you to make men weary? must ye also make my God weary as well?” (Isaiah 7: 13)
What wearies man and God? Evil. And apparently the evil existing within His chosen people – no, not the nation of Israel alone, but any one person whom He selects as His own.
Isaiah says that the child called “God With Us” will “eat butter and honey, that He know how to reprove evil, and choose good.” (Isaiah 7: 15)
Choosing good is what we can’t seem to get right. For this thing, God comes into the world as an infant, to take up our burdens and walk as we walk, to die in our stead so we might live.