Therefore the Lord Himself will give you a sign: Behold, the virgin shall conceive and bear a Son, and shall call His name Immanuel.
God gave King Ahaz permission to ask a sign for himself. He refused and God spoke of the sign He would give.
No one will undermine God.
When He asks something of us, refusal does not change anything.
Refusal does not alter the outcome.
Someone may refuse His offer of salvation but they cannot refuse the outcome of such an action.
No one can refuse to stand before Him in judgment.
No one can refuse Him in reward or condemnation.
Although these words may have some kind of fulfilled meaning in the days of Ahaz it definitely points to a future event fulfilled by Mary, as the virgin, and Jesus as the Messiah and Son. (c.f. Matthew 1:22-23)
Jesus is the ultimate “sign” of God. The entire Bible points to Him.
Don’t refuse Him.